no errors keyword for decode in python 2.6

[blalor]

Attempting to run pex on Python 2.6.8 fails. I had to add -v to see the error, otherwise it just says it can't resolve the requirement.

[root@08b6ba92511a ~]# pex --python=/usr/bin/python2.6 -r fabric -v
pex: Unknown exception encountered: decode() takes no keyword arguments
pex: Traceback (most recent call last):
pex:   File "/usr/lib/python2.6/site-packages/pex/crawler.py", line 110, in execute
pex:     roots, rels = self.crawl_link(self.context, link)
pex:   File "/usr/lib/python2.6/site-packages/pex/crawler.py", line 87, in crawl_link
pex:     return cls.crawl_remote(context, link)
pex:   File "/usr/lib/python2.6/site-packages/pex/crawler.py", line 74, in crawl_remote
pex:     content = context.content(link)
pex:   File "/usr/lib/python2.6/site-packages/pex/http.py", line 122, in content
pex:     return fp.read().decode(encoding, errors='replace')
pex: TypeError: decode() takes no keyword arguments
Traceback (most recent call last):
  File "/usr/bin/pex", line 11, in <module>
    sys.exit(main())
  File "/usr/lib/python2.6/site-packages/pex/bin/pex.py", line 325, in main
    pex_builder = build_pex(args, options)
  File "/usr/lib/python2.6/site-packages/pex/bin/pex.py", line 303, in build_pex
    cache_ttl=options.cache_ttl)
  File "/usr/lib/python2.6/site-packages/pex/resolver.py", line 220, in resolve
    raise Unsatisfiable('Cannot satisfy requirements: %s' % requirement_set[requirement.key])
pex.resolver.Unsatisfiable: Cannot satisfy requirements: [Requirement.parse('fabric')]

[wickman]

Fixed by #46