gistfile1.txt

% mkdir -p demodir/derp

% cat > demodir/derp/testing.py <<EOT
heredoc> print 'this is a test'
heredoc> EOT

% cat > demo.py <<EOT
heredoc> from demodir.derp import testing
heredoc> EOT

% python2 demo.py
Traceback (most recent call last):
  File "demo.py", line 1, in <module>
    from demodir.derp import testing
ImportError: No module named demodir.derp

% python3 demo.py
Traceback (most recent call last):
  File "demo.py", line 1, in <module>
    from demodir.derp import testing
  File "/home/wheaties/dev/init-test/demodir/derp/testing.py", line 1
    print 'this is a test'
                         ^
SyntaxError: invalid syntax

% cat > demodir/derp/testing.py <<EOT
print('this is a test')
EOT                    

% python3 demo.py
this is a test