It was very easy to load plugin files in Python 2:

import imp
my_module = imp.load_source("what.ever", "foo.py")

Unfortunately, this became much more obscure in Python 3.3:

import importlib.machinery
loader = importlib.machinery.SourceFileLoader("what.ever", "foo.py")
my_module = loader.load_module("what.ever")

In Python 3.4 even this has been deprecated. There should be a way (preferable an easy-to-use one) to load a Python module by filename or by stream.