Add option to silence messsage for Python 2.7 deprecation

[pradyunsg]

What's the problem this feature will solve?
There is a feature request to be able to silence Python version related warnings that pip emits (try running pip 19 on Python 2.7 to see what that means).

See #6231 for context.

Describe the solution you'd like
The way we want to handle this request is to add a new flag/command line option, similar to --no-warn-script-location to pip, in pip._internal.cli.cmdoptions.general_group (as named in code) and using that within pip's BaseCommand class for putting the version-based checking under a conditional.

Alternative Solutions

• Maintain status quo
• Piggy back on Add ids (and classes?) to logged messages, to simplify filtering (and explaining?) #6119

Additional context

Additional references:

• See Warn user when installing scripts outside PATH #4553 for how --no-warn-script-locations is implemented.

• where general options are defined

  pip/src/pip/_internal/cli/cmdoptions.py

  Line 775 in 293c91e

  general_group = {

• where general options get added

  pip/src/pip/_internal/cli/base_command.py

  Line 78 in 293c91e

  self.parser.add_option_group(gen_opts)

• where to add conditional

  pip/src/pip/_internal/cli/base_command.py

  Line 139 in 293c91e

  if sys.version_info[:2] == (3, 4):

This is a moderately complex issue that can serve as starting point for anyone who wants to help out with pip's development -- the process of fixing this should be a good introduction to pip's development workflow.

[AdaBehan]

In src/pip/_internal/cli/base_command.py There are three deprecation warnings should we enable silencing all of the or just the 2.7 warning ?

3.4:

"Python 3.4 support has been deprecated. pip 19.1 will be the last one supporting it. Please upgrade your Python as Python 3.4 won't be maintained after March 2019 (cf PEP 429).",

2.7:

"A` future version of pip will drop support for Python 2.7."

2.7 Cpython:

"Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. "

[AdaBehan]

We raise an error if the python version has become deprecation i imagine we want to keep this behavior.

pip/src/pip/_internal/utils/deprecation.py

Lines 90 to 93 in 293c91e

	# Raise as an error if it has to be removed.
	if gone_in is not None and parse(current_version) >= parse(gone_in):
	raise PipDeprecationWarning(message)
	warnings.warn(message, category=PipDeprecationWarning, stacklevel=2)

[victorvpaulo]

I would like to work on this.
Really seems like a good way to start contributing to pip development.

[pradyunsg]

Just the 2.7 ones. All python-version based deprecation warnings.

We'd want to continue raising an exception in the deprecation helper.

[pradyunsg]

Please feel free to work on this @victorvpaulo or @adamRogerson!

[AdaBehan]

@victorvpaulo I was going to have a wack at this but if you need more time ill hold off.

[victorvpaulo]

@adamRogerson I have a implementation for this feature almost ready(#6739), but i could use some help.
The implementation is blocked because some tests are failing, and i can't figure out why.
Would you be interested in helping me with that?
Edit: Finally the tests have passed and the PR is ready for review.

[AdaBehan]

@victorvpaulo Nice work :)

[pradyunsg]

Closed by #6739.