You can set the desired location / language using the module locale. To get English, try installing localeon en_US.
:
bash Ubuntu en_US.utf8
In [1]: import datetime
In [2]: import locale
In [3]: locale.setlocale(locale.LC_ALL,'fr_FR')
Out[3]: 'fr_FR'
In [4]: datetime.datetime(2015,7,1).strftime('%B')
Out[4]: 'juillet'
In [5]: locale.setlocale(locale.LC_ALL,'en_US')
Out[5]: 'en_US'
In [6]: datetime.datetime(2015,7,1).strftime('%B')
Out[6]: 'July'