Python-language-server: Diagnostics should respect `# noqa` and similar comments

[jakebailey]

ptvsd uses # noqa to disable linting for specific lines, for example:

try:
    unicode  # noqa

    def needs_unicode(value):
        return isinstance(value, unicode)  # noqa
except Exception:
    def needs_unicode(value):
        return False

Any diagnostics we output should respect comments like these. I believe there are other ones out there depending on the linter, like #pylint: disable and # NOQA.

[jfthuong]

Linting could be also disabled for a particular warning.

For example, pylint has the following way of locally disabling a warning:

4.1 Is it possible to locally disable a particular message?
    Yes, this feature has been added in Pylint 0.11. 
    This may be done by adding “#pylint: disable=some-message,another-one”
    at the desired block level or at the end of the desired line of code.

[janosh]

This feature would be great to have!

For the record, # noqa also supports disabling specific warnings with # noqa: E731. python-language-server could support that as well.

[jakebailey]

Partial support for this will come in #1272 (catch-all noqa), but we'll need mappings from other tools' codes in order to go further.

[MikhailArkhipov]

https://github.com/microsoft/python-language-server/pull/1272 adds basic support. New issue will be opened for more advanced cases.