fix pants dep inference for pylint_plugins

When pylint_plugins/ is on PYTHONPATH, we cannot use a relative import.
We do not add it to PYTHONPATH in the Makefile, so we need the relative
import. So, use a try/catch block to support both methods until we can
drop the Makefile.

Author: cognifloyd

pants.toml

@@ -174,9 +174,9 @@ source_plugins = [
 ]
 args = [
   # needed in st2* components, runners, packs
-  "--load-plugins=pylint_plugins.api_models",
+  "--load-plugins=api_models",
   # needed in st2* components, runners
-  "--load-plugins=pylint_plugins.db_models",
+  "--load-plugins=db_models",
 ]
 
 [pytest]

pylint_plugins/api_models_test.py

@@ -22,7 +22,12 @@
 
 # merely importing this registers it in astroid
 # so parse() will use our predicate and transform functions.
-from . import api_models
+try:
+    # TODO: remove this once we remove the Makefile
+    from . import api_models
+except ImportError:
+    # pylint_plugins is on PYTHONPATH
+    import api_models
 
 
 def test_skiplist_class_gets_skipped():