Bumped version requirement on pytz

[chrisbrake]

Here you use the utc attribute on the _pytz object:

babel/babel/util.py

Line 304 in 23ca4bf

UTC = _pytz.utc

Which was added in this commit stub42/pytz@ae82fbc

Corrected the version requirement to match the version where that attribute was added.

[chrisbrake]

The failing travis build failed with the error:

$ make test-cov
Traceback (most recent call last):
  File "/home/travis/build/python-babel/babel/scripts/import_cldr.py", line 958, in <module>
    main()
  File "/home/travis/build/python-babel/babel/scripts/import_cldr.py", line 191, in main
    dump_json=bool(options.dump_json)
  File "/home/travis/build/python-babel/babel/scripts/import_cldr.py", line 197, in process_data
    sup = parse(sup_filename)
  File "/opt/python/pypy3.5-5.8.0/lib-python/3/xml/etree/ElementTree.py", line 1217, in parse
    tree.parse(source, parser)
  File "/opt/python/pypy3.5-5.8.0/lib-python/3/xml/etree/ElementTree.py", line 607, in parse
    source = open(source, "rb")
FileNotFoundError: [Errno 2] No such file or directory: '/home/travis/build/python-babel/babel/cldr/core-33.0/common/supplemental/supplementalData.xml'
Traceback (most recent call last):
  File "scripts/download_import_cldr.py", line 104, in <module>
    main()
  File "scripts/download_import_cldr.py", line 100, in main
    common_path])
  File "/opt/python/pypy3.5-5.8.0/lib-python/3/subprocess.py", line 271, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/home/travis/virtualenv/pypy3.5-5.8.0/bin/python', '/home/travis/build/python-babel/babel/scripts/import_cldr.py', '/home/travis/build/python-babel/babel/cldr/core-33.0/common']' returned non-zero exit status 1
make: *** [import-cldr] Error 1

I do not believe that is related to my change.

[akx]

The Travis problem seems like a transient blip. I restarted the affected build, it should go through.

[chrisbrake]

Thanks for restarting the build for me