Subversion test failing in Mac OS

[deveshks]

Environment

• pip version: 20.1.dev0
• Python version: 3.8.2
• OS: Mac OSX Catalina 10.15.4

I have installed pip from the source tree using pip install . in a virtualenv

Description

The test case test_subversion__call_vcs_version listed at https://github.com/pypa/pip/blob/master/tests/unit/test_vcs.py#L430 fails with an assertion error

Expected behavior

The test should pass.

How to Reproduce

Run tox -e py tests/unit/test_vcs.py::test_subversion__call_vcs_version -s to run the specific test in question.

Output

The failure output is as follows

$ tox -e py tests/unit/test_vcs.py::test_subversion__call_vcs_version -s
GLOB sdist-make: /Users/devesh/pip/setup.py
py inst-nodeps: /Users/devesh/pip/.tox/.tmp/package/1/pip-20.1.dev0.zip
py installed: WARNING: Could not generate requirement for distribution -ip 20.1.dev0 (/Users/devesh/pip/.tox/py/lib/python3.8/site-packages): Parse error at "'-ip==20.'": Expected W:(abcd...),apipkg==1.5,atomicwrites==1.3.0,attrs==19.3.0,cffi==1.14.0,coverage==5.0.4,cryptography==2.8,csv23==0.2,execnet==1.7.1,freezegun==0.3.15,mock==4.0.2,more-itertools==8.2.0,pip==20.1.dev0,pluggy==0.13.1,pretend==1.0.9,py==1.8.1,pycparser==2.20,pytest==3.8.2,pytest-cov==2.8.1,pytest-forked==1.1.3,pytest-rerunfailures==6.0,pytest-timeout==1.3.4,pytest-xdist==1.27.0,python-dateutil==2.8.1,PyYAML==5.3.1,scripttest==1.3,setuptools==46.1.3,six==1.14.0,virtualenv==16.7.10,Werkzeug==0.16.0,wheel==0.34.2
py run-test-pre: PYTHONHASHSEED='2829047682'
py run-test-pre: commands[0] | python -c 'import shutil, sys; shutil.rmtree(sys.argv[1], ignore_errors=True)' /Users/devesh/pip/tests/data/common_wheels
py run-test-pre: commands[1] | python /Users/devesh/pip/tools/tox_pip.py wheel -w /Users/devesh/pip/tests/data/common_wheels -r /Users/devesh/pip/tools/requirements/tests-common_wheels.txt
Collecting setuptools>=40.8.0
  Using cached setuptools-46.1.3-py3-none-any.whl (582 kB)
  Saved ./tests/data/common_wheels/setuptools-46.1.3-py3-none-any.whl
Collecting wheel
  Using cached wheel-0.34.2-py2.py3-none-any.whl (26 kB)
  Saved ./tests/data/common_wheels/wheel-0.34.2-py2.py3-none-any.whl
Skipping setuptools, due to already being wheel.
Skipping wheel, due to already being wheel.
py run-test: commands[0] | pytest --timeout 300 tests/unit/test_vcs.py::test_subversion__call_vcs_version
======================================================== test session starts ========================================================
platform darwin -- Python 3.8.2, pytest-3.8.2, py-1.8.1, pluggy-0.13.1
rootdir: /Users/devesh/pip, inifile: setup.cfg
plugins: timeout-1.3.4, rerunfailures-6.0, forked-1.1.3, cov-2.8.1, xdist-1.27.0
timeout: 300.0s
timeout method: signal
timeout func_only: False
collected 1 item                                                                                                                    

tests/unit/test_vcs.py F                                                                                                      [100%]

============================================================= FAILURES ==============================================================
_________________________________________________ test_subversion__call_vcs_version _________________________________________________

    @need_svn
    def test_subversion__call_vcs_version():
        """
        Test Subversion.call_vcs_version() against local ``svn``.
        """
        version = Subversion().call_vcs_version()
        # All Subversion releases since 1.0.0 have used three parts.
>       assert len(version) == 3
E       assert 0 == 3
E        +  where 0 = len(())

tests/unit/test_vcs.py:436: AssertionError
====================================================== short test summary info ======================================================
FAIL tests/unit/test_vcs.py::test_subversion__call_vcs_version
===================================================== 1 failed in 0.29 seconds ======================================================
ERROR: InvocationError for command /Users/devesh/pip/.tox/py/bin/pytest --timeout 300 tests/unit/test_vcs.py::test_subversion__call_vcs_version (exited with code 1)

The error is because in https://github.com/pypa/pip/blob/master/src/pip/_internal/vcs/subversion.py#L204, we always assume that the version string, svn, version will be present in the first line, but that might not always be the case.

$ svn --version 
Warning: Failed to set locale category LC_NUMERIC to en_IN.
Warning: Failed to set locale category LC_TIME to en_IN.
Warning: Failed to set locale category LC_COLLATE to en_IN.
Warning: Failed to set locale category LC_MONETARY to en_IN.
Warning: Failed to set locale category LC_MESSAGES to en_IN.
svn, version 1.13.0 (r1867053)
   compiled Feb 19 2020, 02:08:03 on x86_64-apple-darwin19.3.0

Copyright (C) 2019 The Apache Software Foundation.
This software consists of contributions made by many people;
see the NOTICE file for more information.
Subversion is open source software, see http://subversion.apache.org/

The following repository access (RA) modules are available:

* ra_svn : Module for accessing a repository using the svn network protocol.
  - with Cyrus SASL authentication
  - handles 'svn' scheme
* ra_local : Module for accessing a repository on local disk.
  - handles 'file' scheme
* ra_serf : Module for accessing a repository via WebDAV protocol using serf.
  - using serf 1.3.9 (compiled with 1.3.9)
  - handles 'http' scheme
  - handles 'https' scheme

The following authentication credential caches are available:

* Mac OS X Keychain

[deveshks]

In order to move this self-created issue forward, I have created the PR #7969 and applied the requested changes to the same. Would appreciate reviews about the implementation to move the PR ahead and close this issue.