What version are you running?
2.5
What's the URL of the page containing the problem?
https://example.com/ReviewBoard/r/5202/diff/raw/
What steps will reproduce the problem?

modify settings_local.py, and set DEBUG = True
restart apache2
create a review request by uploading a diff file


What is the expected output? What do you see instead?
A review request is expected to be created. 'Invalid utf8 character' is returned
What operating system are you using? What browser?

Please provide any additional information below.
warnings  

((u'Warning', 1300L, u"Invalid utf8 character string: '803994'"),)
'INSERT INTO diffviewer_rawfilediffdata (binary_hash, binary, compression, extra_data) VALUES (\'033731afc5dd0568f332de3888e8087d42a8949c\', \'BZh91AY&SY\x809\x94

...
Python Path:  

['/var/www/review/conf',

 '/usr/local/lib/python2.7/dist-packages/recaptcha_client-1.0.6-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/mimeparse-0.1.3-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/PIL-1.1.7-py2.7-linux-x86_64.egg',

 '/usr/local/lib/python2.7/dist-packages/pillowfight-0.2-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/distribute-0.7.3-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/django_haystack-2.4.0-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/django_evolution-0.7.5-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/pip-7.1.2-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/Django-1.6.11.1-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/ReviewBoard-2.5-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/Djblets-0.9-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/django_multiselectfield-0.1.3-py2.7.egg',

 '/usr/local/lib/python2.7/dist-packages/MySQL_python-1.2.5-py2.7-linux-x86_64.egg',

 '/usr/lib/python2.7',

 '/usr/lib/python2.7/plat-x86_64-linux-gnu',

 '/usr/lib/python2.7/lib-tk',

 '/usr/lib/python2.7/lib-old',

 '/usr/lib/python2.7/lib-dynload',

 '/usr/local/lib/python2.7/dist-packages',

 '/usr/lib/python2.7/dist-packages']