Pint won't import on Python 2.6 unless the enviornment happens to include unittest2. Should be explicit.

[movermeyer]

On Python 2.6 and pint 0.7.2:

>>> import pint
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/exactEarth/pint/env/lib/python2.6/site-packages/pint/__init__.py", line 19, in <module>
    from .unit import (UnitRegistry, LazyRegistry)
  File "/usr/local/exactEarth/pint/env/lib/python2.6/site-packages/pint/unit.py", line 27, in <module>
    from . import registry_helpers
  File "/usr/local/exactEarth/pint/env/lib/python2.6/site-packages/pint/registry_helpers.py", line 14, in <module>
    from .compat import string_types, zip_longest
  File "/usr/local/exactEarth/pint/env/lib/python2.6/site-packages/pint/compat/__init__.py", line 58, in <module>
    raise Exception("Testing Pint in Python 2.6 requires package 'unittest2'")
Exception: Testing Pint in Python 2.6 requires package 'unittest2'

Except it shouldn't fail since this dependency is only needed when running tests.

If we add it to the tests_require parameter of setup.py

Something like:

tests_require = ['unittest2 ; python_version < '2.7']

and move compatibility lookup into a testsuite/compat/init.py,

then users can import pint on Python 2.6 without having to manually specify additional dependencies in order for it to run.

Pull request coming soon.

[hgrecco]

Thanks for reporting. Fixed by 842e8f2