Fix SiteDir fixture to properly patch sys.path in one place, encapsulating concern and avoiding adding duplicate entries. Fixes #61.

Author: jaraco

importlib_metadata/tests/fixtures.py

@@ -24,11 +24,9 @@
 @contextlib.contextmanager
 def tempdir():
     tmpdir = tempfile.mkdtemp()
-    sys.path[:0] = [tmpdir]
     try:
         yield pathlib.Path(tmpdir)
     finally:
-        sys.path.remove(tmpdir)
         shutil.rmtree(tmpdir)
 
 
@@ -55,7 +53,10 @@ class SiteDir:
     def site_dir():
         with tempdir() as tmp:
             sys.path[:0] = [str(tmp)]
-            yield tmp
+            try:
+                yield tmp
+            finally:
+                sys.path.remove(str(tmp))
 
     def setUp(self):
         self.fixtures = ExitStack()