I met the same problem, and I try the pdb.set_trace() before the error line.
My problem is the package name duplicate with the module name, like:
test
+-- __init__.py
+-- a
¦ +-- __init__.py
¦ +-- test.py
+-- b
+-- __init__.py
and at file a/__init__.py, using from test.b import xxx will cause ImportError: No module named b.