Log Message:
Update to 0.7.3:

0.7.3 (2013-07-02):
  - Do not report undefined name for generator expression and dict or
    set comprehension at class level.
  - Deprecate `Checker.pushFunctionScope` and `Checker.pushClassScope`:
    use `Checker.pushScope` instead.
  - Remove dependency on Unittest2 for the tests.

0.7.2 (2013-04-24):
  - Fix computation of `DoctestSyntaxError.lineno` and `col`.
  - Add boolean attribute `Checker.withDoctest` to ignore doctests.
  - If environment variable `PYFLAKES_NODOCTEST` is set, skip doctests.
  - Environment variable `PYFLAKES_BUILTINS` accepts a comma-separated
    list of additional built-in names.

0.7.1 (2013-04-23):
  - File `bin/pyflakes` was missing in tarball generated with distribute.
  - Fix reporting errors in non-ASCII filenames (Python 2.x).

0.7.0 (2013-04-17):
  - Add --version and --help options.
  - Support `python -m pyflakes` (Python 2.7 and Python 3.x).
  - Add attribute `Message.col` to report column offset.
  - Do not report redefinition of variable for a variable used in a list
    comprehension in a conditional.
  - Do not report redefinition of variable for generator expressions and
    set or dict comprehensions.
  - Do not report undefined name when the code is protected with a
    `NameError` exception handler.
  - Do not report redefinition of variable when unassigning a module imported
    for its side-effect.
  - Support special locals like `__tracebackhide__` for py.test.
  - Support checking doctests.
  - Fix issue with Turkish locale where `'i'.upper() == 'i'` in Python 2.

0.6.1 (2013-01-29):
  - Fix detection of variables in augmented assignments.

0.6.0 (2013-01-29):
  - Support Python 3 up to 3.3, based on the pyflakes3k project.
  - Preserve compatibility with Python 2.5 and all recent versions of Python.
  - Support custom reporters in addition to the default Reporter.
  - Allow function redefinition for modern property construction via
    property.setter/deleter.
  - Fix spurious redefinition warnings in conditionals.
  - Do not report undefined name in __all__ if import * is used.
  - Add WindowsError as a known built-in name on all platforms.
  - Support specifying additional built-ins in the `Checker` constructor.
  - Don't issue Unused Variable warning when using locals() in current scope.
  - Handle problems with the encoding of source files.
  - Remove dependency on Twisted for the tests.
  - Support `python setup.py test` and `python setup.py develop`.
  - Create script using setuptools `entry_points` to support all platforms,
    including Windows.