Fix site.getsitepackages() broken on python2 on debian

Author: freundTech

docs/changelog/2105.bugfix.rst

@@ -0,0 +1 @@
+Fix ``site.getsitepackages()`` broken on python2 on debian - by :user:`freundTech`.

src/virtualenv/create/via_global_ref/builtin/python2/site.py

@@ -19,6 +19,7 @@ def main():
     load_host_site()
     if global_site_package_enabled:
         add_global_site_package()
+    rewrite_getsitepackages()
 
 
 def load_host_site():
@@ -161,4 +162,22 @@ def add_global_site_package():
         site.PREFIXES = orig_prefixes
 
 
+# Debian and it's derivatives patch this function. We undo the damage
+def rewrite_getsitepackages():
+    site = sys.modules["site"]
+
+    orig_getsitepackages = site.getsitepackages
+
+    def getsitepackages():
+        sitepackages = orig_getsitepackages()
+        for prefix in (sys.prefix, sys.exec_prefix):
+            path = os.path.join(prefix, "lib", "python" + sys.version[:3], "site-packages")
+            if path not in sitepackages:
+                sitepackages.insert(0, path)
+
+        return sitepackages
+
+    site.getsitepackages = getsitepackages
+
+
 main()

tests/unit/create/test_creator.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
+import ast
 import difflib
 import gc
 import json
@@ -621,3 +622,16 @@ def test_pth_in_site_vs_PYTHONPATH(tmp_path):
         env=env,
     )
     assert out == "ok\n"
+
+
+def test_getsitepackages(tmp_path):
+    session = cli_run([ensure_text(str(tmp_path))])
+    env_site_packages = [str(session.creator.purelib), str(session.creator.platlib)]
+    out = subprocess.check_output(
+        [str(session.creator.exe), "-c", r"import site; print(site.getsitepackages())"],
+        universal_newlines=True,
+    )
+    site_packages = ast.literal_eval(out)
+
+    for env_site_package in env_site_packages:
+        assert env_site_package in site_packages