Fix Drive install on Linux

$ sudo pip install -U -r https://raw.github.com/nuxeo/nuxeo-drive/master/requirements.txt
(...)
creating build/lib.linux-x86_64-2.7/cx_Freeze/bases
x86_64-linux-gnu-gcc -pthread build/temp.linux-x86_64-2.7/source/bases/Console.o -o build/lib.linux-x86_64-2.7/cx_Freeze/bases/Console -s
(...)
collect2: erreur: ld a retourné 1 code d'état d'exécution

error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

----------------------------------------
Cleaning up...
Command /usr/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip_build_root/cx-Freeze/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-hSSRn9-record/install-record.txt --single-version-externally-managed --compile failed with error code 1 in /tmp/pip_build_root/cx-Freeze
Traceback (most recent call last):
  File "/usr/local/bin/pip", line 9, in <module>
    load_entry_point('pip==1.5.6', 'console_scripts', 'pip')()
  File "/usr/local/lib/python2.7/dist-packages/pip/__init__.py", line 185, in main
    return command.main(cmd_args)
  File "/usr/local/lib/python2.7/dist-packages/pip/basecommand.py", line 161, in main
    text = '\n'.join(complete_log)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 73: ordinal not in range(128)