IOVDbSvc: Remove usage of EndOfBeginRun incident and python cleanup
Two unrelated changes:
- The "EndOfBeginRun" was previously fired by the HLT to force the closing
of the POOL connections. This is no longer required as the HLT is now using
the same mechanism as athenaMP, i.e. it calls
io_finalize
before forking. - Enable flake8 checking during the build and make the python code compliant.