various fixes

- nodestatechange callback must appear after the online attribute
  is changed
- IntRange: move range validation outside of try except
- fixes on some error names
- well defined error message 'no such class' in secop.lib.get_class
- try again 4 times when starting Tcp Server on EADDRINUSE
- fix error handling

Change-Id: I4eee9b79ea8173936b9f5193b87e006ac8fca827
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/26171
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/errors.py

@@ -143,7 +143,7 @@ EXCEPTIONS = dict(
     NoSuchCommand=NoSuchCommandError,
     CommandFailed=CommandFailedError,
     CommandRunning=CommandRunningError,
-    Readonly=ReadOnlyError,
+    ReadOnly=ReadOnlyError,
     BadValue=BadValueError,
     CommunicationFailed=CommunicationFailedError,
     HardwareError=HardwareError,
@@ -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,