Skip uv when running tests.

GH-83 `uv` isn't installed by default in the GitHub Ubuntu-latest
environment, so we can't use it when running tests. We need to figure
out how to get it installed, but for now we'll just change the
script to run tests w/o `uv`.

run

@@ -134,10 +134,12 @@ def main(argv):
     args = parser.parse_args(argv)
 
     global uv_path
-    uv_path = shutil.which('uv')
-    if uv_path is None:
-        print('You need to have `uv` installed to run this script.')
-        sys.exit(2)
+    if args.func != run_tests:
+        # TODO(GH-83): Figure out how to get `uv` installed in the GitHub CI.
+        uv_path = shutil.which('uv')
+        if uv_path is None:
+            print('You need to have `uv` installed to run this script.')
+            sys.exit(2)
 
     global run_cmd
     if 'VIRTUAL_ENV' in os.environ:
@@ -290,7 +292,9 @@ def run_regen(args):
 
 def run_tests(args):
     del args
-    call(run_cmd + ['-m', 'unittest', 'discover', '-p', '*_test.py'])
+    # TODO(GH-83): Figure out how to get `uv` installed on the GitHub CI.
+    # call(run_cmd + ['-m', 'unittest', 'discover', '-p', '*_test.py'])
+    call([sys.executable, '-m', 'unittest', 'discover', '-p', '*_test.py'])
 
 
 def _gen_parser():