UserDict import fails on Python 2.6 if six is too old #376
Description
I just updated planemo, and ran into a dependency problem under Python 2.6:
$ planemo --version
planemo, version 0.20.1.dev0
$ planemo shed_diff -t toolshed tools/ncbi_blast_plus/
Problem loading command shed_diff, exception cannot import name UserDict
Usage: planemo [OPTIONS] COMMAND [ARGS]...
Error: No such command "shed_diff".
The UserDict class moved from Python 2 to 3, which ought to be handled by from six.moves import UserDict as used in planemo_ext/galaxy/util/odict.py, however my version of six is too old:
$ python
Python 2.6.6 (r266:84292, Jul 23 2015, 15:22:56)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from six.moves import UserDict
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: cannot import name UserDict
>>> import six
>>> six.__version__
'1.6.1'
Therefore I think that requirements.txt should set a minimum version of six. The UserDict move was added in version 1.7.0, the current version is 1.10.0.
I manually updated to six v1.10.0 and reinstalled planemo, and this works again.