Show warnings from pkgdb_to_bzl.py script

Author: avdv

haskell/private/pkgdb_to_bzl.bzl

@@ -19,6 +19,9 @@ def pkgdb_to_bzl(repository_ctx, paths, libdir):
     ])
     if result.return_code:
         fail("Error executing pkgdb_to_bzl.py: {stderr}".format(stderr = result.stderr))
+    elif result.stderr:
+        # print any warnings from pkgdb_to_bzl.py
+        print(result.stderr)
 
     result_dict = json.decode(result.stdout)