Fixed Python 3.1 and 3.2 support by removing unicode literals

[msiedlarek]

This fix comes at a price - it introduces tiny but unavoidable compatibility module with one function replacing unicode literal which doesn't work in Python 3.1-3.2 (brought back in Python 3.3 by PEP 414). I believe though, that support for two modern Python versions, packaged in many of current stable Linux distributions, is worth it.

The compatibility code has been shamelessly copied from zope.schema.

[chrisrossi]

Can you write a test that exposes the problem in 3.2?

[msiedlarek]

It would be something like import pyramid_layout.zcml wrapped up in a TestCase, but sure, why not :)

[msiedlarek]

You can test it by checking out the current master and copying this file:

https://github.com/msiedlarek/pyramid_layout/blob/python3.2-support/pyramid_layout/tests/test_zcml.py

to pyramid_layout/tests directory and executing the tests.

On Python 3.2 for example the test will fail like this:

(env)user@host:~/pyramid_layout$ python --version
Python 3.2.3
(env)user@host:~/pyramid_layout$ python setup.py nosetests
running nosetests
running egg_info
writing requirements to pyramid_layout.egg-info/requires.txt
writing pyramid_layout.egg-info/PKG-INFO
writing top-level names to pyramid_layout.egg-info/top_level.txt
writing dependency_links to pyramid_layout.egg-info/dependency_links.txt
writing manifest file 'pyramid_layout.egg-info/SOURCES.txt'
running build_ext
.................................E
======================================================================
ERROR: #14 Unicode literals in `zcml` module
----------------------------------------------------------------------
Traceback (most recent call last):
  File "path/to/pyramid_layout/pyramid_layout/tests/test_zcml.py", line 25, in test_unicode_literals
    import pyramid_layout.zcml #pragma NO COVERAGE
  File "path/to/pyramid_layout/pyramid_layout/zcml.py", line 10
    title=u"The interface or class this panel is for.",
                                                     ^
SyntaxError: invalid syntax

Name                               Stmts   Miss  Cover   Missing
----------------------------------------------------------------
pyramid_layout                         1      0   100%   
pyramid_layout.config                183      0   100%   
pyramid_layout.interfaces              5      0   100%   
pyramid_layout.layout                 46      0   100%   
pyramid_layout.panel                  18      0   100%   
pyramid_layout.tests                   0      0   100%   
pyramid_layout.tests.test_config     416      0   100%   
pyramid_layout.tests.test_layout     103      0   100%   
pyramid_layout.tests.test_panel       44      0   100%   
pyramid_layout.tests.test_zcml         2      0   100%   
----------------------------------------------------------------
TOTAL                                818      0   100%   
----------------------------------------------------------------------
Ran 34 tests in 0.070s

FAILED (errors=1)