Add workarounds for pypy on Debian

Work around https://bugs.debian.org/962654 by reinstalling pip in the
virutalenv before installing dependencies for pypy or pypy3.

Work around pypa/pip#8653 by using a version
of pip prior to 20.2 for pypy.

FIXME: This may reinstall pip 0 or more times depending on the package
dependencies (e.g. for pyproject.toml build requires, tox deps, package
deps).  No config option for post-create commands.  May need to create a
tox hook package to do this properly.

Signed-off-by: Kevin Locke <[email protected]>

tox-pip-install.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python
+# This file is part of packagename <https://github.com/kevinoid/packagename>
+# Made available under CC0 1.0 Universal, see LICENSE.txt
+# Copyright 2019-2020 Kevin Locke <[email protected]>
+"""
+Script to reinstall pip before running `pip install`.
+
+Workaround for https://bugs.debian.org/962654
+"""
+
+import os
+import sys
+
+# Must be invoked with pip package (optionally version-constrained) as first
+# argument, install options+packages as subsequent options.
+if len(sys.argv) < 3 or not sys.argv[1].startswith("pip"):
+    sys.stderr.write(
+        'Usage: ' + sys.argv[0] + ' <pip version> [options] <packages...>\n')
+    sys.exit(1)
+
+# Workaround is only needed on Debian (and derivatives)
+if os.path.exists('/etc/debian_version'):
+    pip_exit_code = os.spawnl(
+        os.P_WAIT,
+        sys.executable,
+        sys.executable,
+        '-m',
+        'pip',
+        'install',
+        '--force',
+        sys.argv[1])
+    if pip_exit_code != 0:
+        sys.exit(pip_exit_code)
+
+os.execv(
+    sys.executable,
+    [sys.executable, '-m', 'pip', 'install'] + sys.argv[2:])

tox.ini

@@ -33,3 +33,12 @@ commands =
     pyroma .
     vulture --exclude */docs/*,*/tests/*,*/.tox/*,*/.venv*/* .
     black --check --diff .
+
+[testenv:pypy]
+# Reinstall pip to work around https://bugs.debian.org/962654
+# Use version 20.1.1 to work around https://github.com/pypa/pip/issues/8653
+install_command = python tox-pip-install.py pip==20.1.1 {opts} {packages}
+
+[testenv:pypy3]
+# Reinstall pip to work around https://bugs.debian.org/962654
+install_command = python tox-pip-install.py pip {opts} {packages}