Pylint configuration is busted

Summary

It seems like we should be getting certain warnings from pylint about our codebase but we aren't. I think this is happening because we messed up our pylint configuration when we moved sources into a src directory (I can take the blame for that).

We currently invoke pylint as pylint src/buildstream tests. Locally, I tried pylint src tests by accident and got a few warnings on master, which was surprising. Later I realized that my invocation was more correct and the warnings were real things that we need to fix.

Steps to reproduce

# This is what we currentl do - everything's fine!
(lint) root@2428e3458936:/src# pylint src/buildstream tests

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Your code has been rated at 10.00/10 (previous run: 9.99/10, +0.01)

# This is what I tried and got new warnings
(lint) root@2428e3458936:/src# pylint src tests
************* Module buildstream.plugins.sources.patch
src/buildstream/plugins/sources/patch.py:83:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
************* Module buildstream.plugins.sources.bzr
src/buildstream/plugins/sources/bzr.py:104:4: W0221: Parameters differ from overridden 'track' method (arguments-differ)
src/buildstream/plugins/sources/bzr.py:118:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
************* Module buildstream.plugins.sources.tar
src/buildstream/plugins/sources/tar.py:83:8: W0201: Attribute '__permission' defined outside __init__ (attribute-defined-outside-init)
************* Module buildstream.plugins.sources.local
src/buildstream/plugins/sources/local.py:78:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
src/buildstream/plugins/sources/local.py:42:0: W0611: Unused utils imported from buildstream (unused-import)
************* Module buildstream.plugins.sources._downloadablefilesource
src/buildstream/plugins/sources/_downloadablefilesource.py:114:4: W0221: Parameters differ from overridden 'track' method (arguments-differ)
src/buildstream/plugins/sources/_downloadablefilesource.py:131:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
************* Module buildstream.plugins.sources.pip
src/buildstream/plugins/sources/pip.py:158:4: W0221: Parameters differ from overridden 'track' method (arguments-differ)
src/buildstream/plugins/sources/pip.py:180:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
************* Module buildstream.plugins.sources.workspace
src/buildstream/plugins/sources/workspace.py:61:4: W0221: Parameters differ from overridden 'track' method (arguments-differ)
src/buildstream/plugins/sources/workspace.py:91:4: W0221: Parameters differ from overridden 'fetch' method (arguments-differ)
src/buildstream/plugins/sources/workspace.py:38:0: W0611: Unused import os (unused-import)
src/buildstream/plugins/sources/workspace.py:40:0: W0611: Unused CasBasedDirectory imported from buildstream.storage._casbaseddirectory (unused-import)
src/buildstream/plugins/sources/workspace.py:42:0: W0611: Unused utils imported from buildstream (unused-import)

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Your code has been rated at 9.99/10

What is the current bug behavior?

Pylint warnings get hidden.

What is the expected correct behavior?

Pylint warnings are reported correctly.