Pylint doesn't take anymore the default rcfile if the rcfile specified on the command line doesn't exist (#1768)

This is a more permissive regex which also allows digits.

Fixes ``pylint disable=fixme` directives ignored for comments following the last statement in a file (#1740)

Fixes #1681

Add of a test on the presence of = in the line. Return None instead of Return to avoid inconsistent return statement

Add of 2 very long lines with a disable=fixme directive that should not deactivate emission of line-too-long messages.

Modifying line_too_long.py to add test checking that another directive thant 'line-too-long' doesn't deactivate the emission of 'line-too-long' message

Close #1756

Whilst working on the Reproducible Builds effort [0], we noticed
that pylint could not be built reproducibly.

This is due to the documentation generator iterating over the filesystem
in a nondeterminstic order and then iterating over an internal,
nondeterminstic, data structure.

This was originally filed in Debian as #883913.

 [0] https://reproducible-builds.org/
 [1] https://bugs.debian.org/883913



Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>

Change log entry added in #1733 was accidentally removed in commit
996b3fb5 in PR #1726

Adding changelog entry back.

Fixes: #1301

This TODO was resolved in: https://github.com/PyCQA/pylint/pull/1733#pullrequestreview-75930778

Resolves: #1301

Shallow copy of os.environ doesn't work as people may expect. os.environ
is not a dict object but rather a proxy object, so any changes made
on the copy may have unexpected effects on os.environ

Instead of copy.copy(os.environ) method os.environ.copy() should be
used.

Message id is: `shallow-copy-environ`

See https://bugs.python.org/issue15373 for details.

Resolves: #1301

* Extend trailing-comma-tuple check to more complex assignments

The previous implementation was too conservative with looking for
previous tokens associated with assignment: It looked only
at the immediately previous token, causing 'a = (5),' to not be
caught.

Now The current implementation backtracks to the start of the line
to find an assignment substring.

Fixes issue #1713