Fix run_mojo_python_tests devtools path missed in the rename.

TBR=qsr@chromium.org

Review URL: https://codereview.chromium.org/1124023003
diff --git a/mojo/tools/run_mojo_python_tests.py b/mojo/tools/run_mojo_python_tests.py
index 03336c1..d18baf4 100755
--- a/mojo/tools/run_mojo_python_tests.py
+++ b/mojo/tools/run_mojo_python_tests.py
@@ -16,7 +16,7 @@
       # Tests of "mopy" python tools code.
       os.path.join('mojo', 'tools', 'mopy'),
       # Tests of python code in devtools.
-      os.path.join('mojo', 'devtools', 'common', 'pylib')
+      os.path.join('mojo', 'devtools', 'common', 'devtoolslib')
   ]
 
   for test_dir in test_dir_list: