tests: report installed versions of common packages

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

pyproject.toml

@@ -48,6 +48,7 @@ docs = [
 ]
 test = [
   "filelock >= 3",
+  'importlib-metadata; python_version<"3.8"',
   "pytest >= 6.2.4",
   "pytest-cov >= 2.12",
   "pytest-mock >= 2",

tests/conftest.py

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: MIT
 
+import contextlib
 import os
 import os.path
 import shutil
@@ -12,6 +13,11 @@
 
 import build.env
 
+if sys.version_info < (3, 8):
+    import importlib_metadata as metadata
+else:
+    from importlib import metadata
+
 
 def pytest_addoption(parser):
     os.environ['PYTHONWARNINGS'] = 'ignore:DEPRECATION::pip._internal.cli.base_command'  # for when not run within tox
@@ -109,3 +115,26 @@ def tmp_dir():
 @pytest.fixture(autouse=True)
 def force_venv(mocker):
     mocker.patch.object(build.env, '_should_use_virtualenv', lambda: False)
+
+
+def pytest_report_header() -> str:
+    interesting_packages = [
+        'build',
+        'colorama',
+        'filelock',
+        'packaging',
+        'pip',
+        'pyproject_hooks',
+        'setuptools',
+        'tomli',
+        'virtualenv',
+        'wheel',
+    ]
+    valid = []
+    for package in interesting_packages:
+        with contextlib.suppress(ModuleNotFoundError):
+            valid.append(f'{package}=={metadata.version(package)}')
+    reqs = ' '.join(valid)
+    pkg_line = f'installed packages of interest: {reqs}'
+
+    return '\n'.join([pkg_line])