Fix tests for Windows.

Author: jsirois

tests/test_main.py

@@ -63,7 +63,7 @@ def assert_version(
     expected_version,  # type: str
 ):
     # type: (...) -> None
-    output = get_output(args=args + ["--version"])
+    output = get_output(args=[sys.executable] + args + ["--version"])
     assert expected_version == output.strip()