package/python-aenum: drop test_v3.py file for python 2.x to fix pycompile issue

package/python-aenum: drop test_v3.py file for python 2.x to fix pycompile issue

Fixes:
http://autobuild.buildroot.net/results/4ca459d54545c0e20b0f0cdc63bd81844ecd7f36/

aenum has conditional logic to load python 3.x code located in test_v3.py:

if pyver >= 3.0:
    from aenum.test_v3 import TestEnumV3, TestOrderV3, TestNamedTupleV3

And contains logic in setup.py to drop that file during setup.py install if
building for python 2.x:

py3_only = ('aenum/test_v3.py', )
..
if __name__ == '__main__':
    if 'install' in sys.argv:
        import os, sys
	..
        if sys.version_info[0] != 3:
            for file in py3_only:
                try:
                    os.unlink(file)

But this doesn't work in Buildroot as pkg-python.dk first does setup.py
build (which copies test_v3.py to the build directory) before setup.py
install, so test_v3.py gets installed, leading to errors from pycompile:

error:   File "/usr/lib/python2.7/site-packages/aenum/test_v3.py", line 12
    class MagicAutoNumberEnum(Enum, settings=AutoNumber):
                                            ^
SyntaxError: invalid syntax

As a workaround, add a hook to drop it from the target directory when
building for python 2.x.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>