Adding package to setuptools package list (using absolute imports) for Travis and Appveyor

Question

I am porting a library to python 3 and keeping it compatible with python 2.

I have a directory structure like this:

mypackage/
    lib/
    engines/
    __init__.py
    setup.py
    <other_dirs>/

I want the setup to recognize mypackage as a package when I call python setup.py install in the mypackage directory.

So I set packages = ["mypackage"]. My local build passes, but the builds on Travis and Appveyor fail with the error:

Traceback (most recent call last):
  File "setup.py", line 26, in <module>
    from mypackage import VERSION
ImportError: No module named mypackage

(The VERSION variable is defined in __init__.py)

I am using python2 with from __future__ import absolute_import to maintain Python 3 compatibility.

Any idea how I can make the travis and appveyor build systems recognize my package? I found a similar question where the answer was to add a symlink to TRAVIS_BUILD_DIR for Travis. Nothing on Appveyor.