update to changes from mlz repo

- bug fixes in error.py
- add from * to raise statements
- fix py35 compatibility
- finalize omit_unchanged_within feature
- fix follwup bug (missing Param.override) in proxy.py

Change-Id: I621c01a0d5e1ec6696fb06f39666f3316fb53649

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()