Using a modern PEP8 linter detects errors/warnings

Summary

The job to test this is using a deprecated version of the library (pep8 instead pycodestyle), so a lot of error/warnings are not being handled

What is the current bug behavior?

There are some PEP8 errors/warnings

What is the expected correct behavior?

• Error/warnings should be fixed or silenced
• pycodestyle should be used instead pep8

Relevant logs and/or screenshots

$ pycodestyle --first --select E,W --statistics -qq --exclude=fuse.py,doc/source/conf.py,*_pb2.py,*_pb2_grpc.py --max-line-length=119 | sort -s -n -k 1,1
1       E722 do not use bare 'except'
3       E741 ambiguous variable name 'l'
5       E305 expected 2 blank lines after class or function definition, found 1
40      W605 invalid escape sequence '\s'
75      W504 line break after binary operator

Possible fixes

I have started !638 (merged); others can submit fixes as well though

• BuildStream version affected: master