fix issues raising pylint warnings

+ small bug fixes

Change-Id: Ib63bf13ad06446d3ec3b8cd0b16f9426cef9e3f4

secop/protocol/interface/tcp.py

@@ -26,6 +26,7 @@ import socketserver
 import sys
 import threading
 import time
+import errno
 
 from secop.datatypes import BoolType, StringType
 from secop.errors import SECoPError
@@ -192,9 +193,9 @@ class TCPServer(socketserver.ThreadingTCPServer):
                     self, ('0.0.0.0', port), TCPRequestHandler, bind_and_activate=True)
                 break
             except OSError as e:
-                if e.args[0] == 98:  # address already in use
+                if e.args[0] == errno.EADDRINUSE:  # address already in use
                     # this may happen despite of allow_reuse_address
-                    time.sleep(0.3 * (1 << ntry))
+                    time.sleep(0.3 * (1 << ntry))  # max accumulated sleep time: 0.3 * 31 = 9.3 sec
                 else:
                     self.log.error('could not initialize TCP Server: %r' % e)
                     raise