diff --git a/secop/errors.py b/secop/errors.py
index 368ad0f..c50cbac 100644
--- a/secop/errors.py
+++ b/secop/errors.py
@@ -25,7 +25,7 @@
 class SECoPError(RuntimeError):
 
     def __init__(self, *args, **kwds):
-        RuntimeError.__init__(self)
+        super().__init__()
         self.args = args
         for k, v in list(kwds.items()):
             setattr(self, k, v)
@@ -151,7 +151,8 @@ EXCEPTIONS = dict(
     IsError=IsErrorError,
     Disabled=DisabledError,
     SyntaxError=ProtocolError,
-    NotImplementedError=NotImplementedError,
+    NotImplemented=NotImplementedError,
+    ProtocolError=ProtocolError,
     InternalError=InternalError,
     # internal short versions (candidates for spec)
     Protocol=ProtocolError,
diff --git a/secop/gui/cfg_editor/mainwindow.py b/secop/gui/cfg_editor/mainwindow.py
index 099686c..937b4f5 100644
--- a/secop/gui/cfg_editor/mainwindow.py
+++ b/secop/gui/cfg_editor/mainwindow.py
@@ -39,7 +39,7 @@ COMMENT = 'comment'
 class MainWindow(QMainWindow):
 
     def __init__(self, file_path=None, parent=None):
-        QMainWindow.__init__(self, parent)
+        super().__init__(parent)
         loadUi(self, 'mainwindow.ui')
         self.tabWidget.currentChanged.connect(self.tab_relevant_btns_disable)
         if file_path is None:
diff --git a/secop/gui/cfg_editor/node_display.py b/secop/gui/cfg_editor/node_display.py
index 300d55c..6ecc95d 100644
--- a/secop/gui/cfg_editor/node_display.py
+++ b/secop/gui/cfg_editor/node_display.py
@@ -26,7 +26,7 @@ from secop.gui.qt import QHBoxLayout, QSizePolicy, QSpacerItem, Qt, QWidget
 
 class NodeDisplay(QWidget):
     def __init__(self, file_path=None, parent=None):
-        QWidget.__init__(self, parent)
+        super().__init__(parent)
         loadUi(self, 'node_display.ui')
         self.saved = bool(file_path)
         self.created = self.tree_widget.set_file(file_path)
diff --git a/secop/gui/cfg_editor/tree_widget_item.py b/secop/gui/cfg_editor/tree_widget_item.py
index 948d891..20b41b2 100644
--- a/secop/gui/cfg_editor/tree_widget_item.py
+++ b/secop/gui/cfg_editor/tree_widget_item.py
@@ -44,7 +44,7 @@ class TreeWidgetItem(QTreeWidgetItem):
         the datatype passed onto ValueWidget should be on of secop.datatypes"""
         # TODO: like stated in docstring the datatype for parameters and
         #  properties must be found out through their object
-        QTreeWidgetItem.__init__(self, parent)
+        super().__init__(parent)
         self.kind = kind
         self.name = name
         self.class_object = class_object
@@ -129,7 +129,7 @@ class ValueWidget(QWidget):
 
     def __init__(self, name='', value='', datatype=None, kind='', parent=None):
         # TODO: implement: change module/interface class
-        QWidget.__init__(self, parent)
+        super().__init__(parent)
         self.datatype = datatype
         self.layout = QVBoxLayout()
         self.name_label = QLabel(name)
@@ -205,7 +205,7 @@ class ValueWidget(QWidget):
 
 class ChangeNameDialog(QDialog):
     def __init__(self, current_name='', invalid_names=None, parent=None):
-        QWidget.__init__(self, parent)
+        super().__init__(parent)
         loadUi(self, 'change_name_dialog.ui')
         self.invalid_names = invalid_names
         self.name.setText(current_name)
diff --git a/secop/gui/cfg_editor/widgets.py b/secop/gui/cfg_editor/widgets.py
index 577ac29..6c866d4 100644
--- a/secop/gui/cfg_editor/widgets.py
+++ b/secop/gui/cfg_editor/widgets.py
@@ -31,7 +31,7 @@ from secop.gui.cfg_editor.utils import get_all_items, \
     get_props, loadUi, set_name_edit_style, setActionIcon
 from secop.gui.qt import QComboBox, QDialog, QDialogButtonBox, QLabel, \
     QLineEdit, QMenu, QPoint, QSize, QStandardItem, QStandardItemModel, \
-    Qt, QTabBar, QTextEdit, QTreeView, QTreeWidget, QWidget, pyqtSignal
+    Qt, QTabBar, QTextEdit, QTreeView, QTreeWidget, pyqtSignal
 
 NODE = 'node'
 MODULE = 'module'
@@ -47,7 +47,7 @@ class TreeWidget(QTreeWidget):
     add_canceled = pyqtSignal()
 
     def __init__(self, parent=None):
-        QTreeWidget.__init__(self, parent)
+        super().__init__(parent)
         self.file_path = None
         self.setIconSize(QSize(24, 24))
         self.setSelectionMode(QTreeWidget.SingleSelection)
@@ -335,7 +335,7 @@ class AddDialog(QDialog):
         """Notes:
             self.get_value: is mapped to the specific method for getting
                             the value from self.value"""
-        QWidget.__init__(self, parent)
+        super().__init__(parent)
         loadUi(self, 'add_dialog.ui')
         self.setWindowTitle('add %s' % kind)
         self.kind = kind
@@ -402,7 +402,7 @@ class AddDialog(QDialog):
 
 class TabBar(QTabBar):
     def __init__(self, parent=None):
-        QTabBar.__init__(self, parent)
+        super().__init__(parent)
         self.setContextMenuPolicy(Qt.CustomContextMenu)
         self.context_pos = QPoint(0, 0)
         self.menu = QMenu()
@@ -436,7 +436,7 @@ class TabBar(QTabBar):
 
 class TreeComboBox(QComboBox):
     def __init__(self, value_dict, parent=None):
-        QComboBox.__init__(self, parent)
+        super().__init__(parent)
         self.tree_view = QTreeView()
         self.tree_view.setHeaderHidden(True)
         self.tree_view.expanded.connect(self.resize_length)
diff --git a/secop/gui/mainwindow.py b/secop/gui/mainwindow.py
index 3399eba..11d417e 100644
--- a/secop/gui/mainwindow.py
+++ b/secop/gui/mainwindow.py
@@ -44,7 +44,7 @@ class QSECNode(QObject):
     logEntry = pyqtSignal(str)
 
     def __init__(self, uri, parent=None):
-        QObject.__init__(self, parent)
+        super().__init__(parent)
         self.conn = conn = secop.client.SecopClient(uri)
         conn.validate_data = True
         self.log = conn.log
@@ -83,10 +83,7 @@ class QSECNode(QObject):
         return self.conn.getParameter(module, parameter, True)
 
     def execCommand(self, module, command, argument):
-        try:
-            return self.conn.execCommand(module, command, argument)
-        except Exception as e:
-            return 'ERROR: %r' % e, {}
+        return self.conn.execCommand(module, command, argument)
 
     def queryCache(self, module):
         return {k: Value(*self.conn.cache[(module, k)])
@@ -115,7 +112,7 @@ class QSECNode(QObject):
 
 class MainWindow(QMainWindow):
     def __init__(self, hosts, parent=None):
-        super(MainWindow, self).__init__(parent)
+        super().__init__(parent)
 
         loadUi(self, 'mainwindow.ui')
 
diff --git a/secop/gui/miniplot.py b/secop/gui/miniplot.py
index 0e43318..15e56ac 100644
--- a/secop/gui/miniplot.py
+++ b/secop/gui/miniplot.py
@@ -160,7 +160,7 @@ class MiniPlotFitCurve(MiniPlotCurve):
         return float('-inf')
 
     def __init__(self, formula, params):
-        super(MiniPlotFitCurve, self).__init__()
+        super().__init__()
         self.formula = formula
         self.params = params
 
@@ -193,7 +193,7 @@ class MiniPlot(QWidget):
     autoticky = True
 
     def __init__(self, parent=None):
-        QWidget.__init__(self, parent)
+        super().__init__(parent)
         self.xmin = self.xmax = None
         self.ymin = self.ymax = None
         self.curves = []
diff --git a/secop/gui/modulectrl.py b/secop/gui/modulectrl.py
index 0fe5210..16553fe 100644
--- a/secop/gui/modulectrl.py
+++ b/secop/gui/modulectrl.py
@@ -32,7 +32,7 @@ from secop.gui.valuewidgets import get_widget
 
 class CommandDialog(QDialog):
     def __init__(self, cmdname, argument, parent=None):
-        super(CommandDialog, self).__init__(parent)
+        super().__init__(parent)
         loadUi(self, 'cmddialog.ui')
 
         self.setWindowTitle('Arguments for %s' % cmdname)
@@ -58,7 +58,7 @@ class CommandDialog(QDialog):
         return True, self.widgets[0].get_value()
 
     def exec_(self):
-        if super(CommandDialog, self).exec_():
+        if super().exec_():
             return self.get_value()
         return None
 
@@ -71,16 +71,17 @@ def showCommandResultDialog(command, args, result, extras=''):
     m.exec_()
 
 
-def showErrorDialog(error):
+def showErrorDialog(command, args, error):
     m = QMessageBox()
-    m.setText('Error %r' % error)
+    args = '' if args is None else repr(args)
+    m.setText('calling: %s(%s)\nraised %r' % (command, args, error))
     m.exec_()
 
 
 class ParameterGroup(QWidget):
 
     def __init__(self, groupname, parent=None):
-        super(ParameterGroup, self).__init__(parent)
+        super().__init__(parent)
         loadUi(self, 'paramgroup.ui')
 
         self._groupname = groupname
@@ -112,7 +113,7 @@ class ParameterGroup(QWidget):
 class CommandButton(QPushButton):
 
     def __init__(self, cmdname, cmdinfo, cb, parent=None):
-        super(CommandButton, self).__init__(parent)
+        super().__init__(parent)
 
         self._cmdname = cmdname
         self._argintype = cmdinfo['datatype'].argument   # single datatype
@@ -140,7 +141,7 @@ class CommandButton(QPushButton):
 class ModuleCtrl(QWidget):
 
     def __init__(self, node, module, parent=None):
-        super(ModuleCtrl, self).__init__(parent)
+        super().__init__(parent)
         loadUi(self, 'modulectrl.ui')
         self._node = node
         self._module = module
@@ -161,10 +162,9 @@ class ModuleCtrl(QWidget):
         try:
             result, qualifiers = self._node.execCommand(
                 self._module, command, args)
-        except TypeError:
-            result = None
-            qualifiers = {}
-            # XXX: flag missing data report as error
+        except Exception as e:
+            showErrorDialog(command, args, e)
+            return
         if result is not None:
             showCommandResultDialog(command, args, result, qualifiers)
 
diff --git a/secop/gui/params/__init__.py b/secop/gui/params/__init__.py
index 60da285..f2162fe 100644
--- a/secop/gui/params/__init__.py
+++ b/secop/gui/params/__init__.py
@@ -39,7 +39,7 @@ class ParameterWidget(QWidget):
                  initvalue=None,
                  readonly=True,
                  parent=None):
-        super(ParameterWidget, self).__init__(parent)
+        super().__init__(parent)
         self._module = module
         self._paramcmd = paramcmd
         self._datatype = datatype
@@ -82,7 +82,6 @@ class GenericParameterWidget(ParameterWidget):
         else:
             value = fmtstr % (value.value,)
         self.currentLineEdit.setText(value)
-        # self.currentLineEdit.setText(str(value))
 
 
 class EnumParameterWidget(GenericParameterWidget):
diff --git a/secop/properties.py b/secop/properties.py
index 97a6c45..047c147 100644
--- a/secop/properties.py
+++ b/secop/properties.py
@@ -24,24 +24,12 @@
 
 
 import inspect
-import sys
 
 from secop.errors import BadValueError, ConfigError, ProgrammingError
+from secop.lib.py35compat import Object
 
 
-class HasDescriptorMeta(type):
-    def __new__(cls, name, bases, attrs):
-        newtype = type.__new__(cls, name, bases, attrs)
-        if sys.version_info < (3, 6):
-            # support older python versions
-            for key, attr in attrs.items():
-                if hasattr(attr, '__set_name__'):
-                    attr.__set_name__(newtype, key)
-            newtype.__init_subclass__()
-        return newtype
-
-
-class HasDescriptors(metaclass=HasDescriptorMeta):
+class HasDescriptors(Object):
     @classmethod
     def __init_subclass__(cls):
         # when migrating old style declarations, sometimes the trailing comma is not removed
@@ -142,12 +130,6 @@ class HasProperties(HasDescriptors):
     @classmethod
     def __init_subclass__(cls):
         super().__init_subclass__()
-        # raise an error when an attribute is a tuple with one single descriptor as element
-        # when migrating old style declarations, sometimes the trailing comma is not removed
-        bad = [k for k, v in cls.__dict__.items()
-               if isinstance(v, tuple) and len(v) == 1 and hasattr(v[0], '__set_name__')]
-        if bad:
-            raise ProgrammingError('misplaced trailing comma after %s.%s' % (cls.__name__, '/'.join(bad)))
         properties = {}
         # using cls.__bases__ and base.propertyDict for this would fail on some multiple inheritance cases
         for base in reversed(cls.__mro__):
diff --git a/secop/protocol/dispatcher.py b/secop/protocol/dispatcher.py
index 0273865..7d9f7ff 100644
--- a/secop/protocol/dispatcher.py
+++ b/secop/protocol/dispatcher.py
@@ -60,12 +60,11 @@ def make_update(modulename, pobj):
 
 
 class Dispatcher:
-
-    OMIT_UNCHANGED_WITHIN = 1  # do not send unchanged updates within 1 sec
-
     def __init__(self, name, logger, options, srv):
         # to avoid errors, we want to eat all options here
         self.equipment_id = options.pop('id', name)
+        # time interval for omitting updates of unchanged values
+        self.omit_unchanged_within = options.pop('omit_unchanged_within', 0.1)
         self.nodeprops = {}
         for k in list(options):
             self.nodeprops[k] = options.pop(k)
@@ -84,7 +83,6 @@ class Dispatcher:
         self._subscriptions = {}
         self._lock = threading.RLock()
         self.restart = srv.restart
-        self.shutdown = srv.shutdown
 
     def broadcast_event(self, msg, reallyall=False):
         """broadcasts a msg to all active connections
diff --git a/secop/protocol/interface/tcp.py b/secop/protocol/interface/tcp.py
index 417db97..a41f4b4 100644
--- a/secop/protocol/interface/tcp.py
+++ b/secop/protocol/interface/tcp.py
@@ -202,3 +202,11 @@ class TCPServer(socketserver.ThreadingTCPServer):
         if ntry:
             self.log.warning('tried again %d times after "Address already in use"' % ntry)
         self.log.info("TCPServer initiated")
+
+    # py35 compatibility
+    if not hasattr(socketserver.ThreadingTCPServer, '__exit__'):
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            self.server_close()
diff --git a/secop/proxy.py b/secop/proxy.py
index d4d3a2a..5d01401 100644
--- a/secop/proxy.py
+++ b/secop/proxy.py
@@ -182,7 +182,7 @@ def proxy_class(remote_class, name=None):
 
     for aname, aobj in rcls.accessibles.items():
         if isinstance(aobj, Parameter):
-            pobj = aobj.override(poll=False, handler=None, needscfg=False)
+            pobj = aobj.merge(dict(poll=False, handler=None, needscfg=False))
             attrs[aname] = pobj
 
             def rfunc(self, pname=aname):