Add test for python_venv language

testing/util.py

@@ -78,6 +78,20 @@ xfailif_no_symlink = pytest.mark.xfail(
 )
 
 
+def supports_venv():  # pragma: no cover (platform specific)
+    try:
+        __import__('ensurepip')
+        __import__('venv')
+        return True
+    except ImportError:
+        return False
+
+
+xfailif_no_venv = pytest.mark.xfail(
+    not supports_venv(), reason='Does not support venv module',
+)
+
+
 def run_opts(
         all_files=False,
         files=(),