Monkey patch 'django.utils.translation'

Modify Django's translation library, such that the gettext family of
functions return an empty string when attempting to translate a
falsey value. This overrides the default behavior [0]:
> It is convention with GNU gettext to include meta-data as the
> translation for the empty string.

This patch provides a holistic solution to replace the current piecemeal
approach [1][2].

Affected Methods:
    - gettext
    - ugettext

[0] https://docs.python.org/2.7/library/gettext.html#the-gnutranslations-class
[1] bad803e451
[2] https://github.com/edx/edx-platform/pull/4653

common/djangoapps/monkey_patch/django_utils_translation.py

@@ -0,0 +1,91 @@
+"""
+Monkey-patch `django.utils.translation` to not dump header info
+
+Modify Django's translation module, such that the *gettext functions
+always return an empty string when attempting to translate an empty
+string. This overrides the default behavior [0]:
+> It is convention with GNU gettext to include meta-data as the
+> translation for the empty string.
+
+Affected Methods:
+    - gettext
+    - ugettext
+
+Note: The *ngettext and *pgettext functions are intentionally omitted,
+as they already behave as expected. The *_lazy functions are implicitly
+patched, as they wrap their nonlazy equivalents.
+
+Django's translation module contains a good deal of indirection. For us
+to patch the module with our own functions, we have to patch
+`django.utils.translation._trans`. This ensures that the patched
+behavior will still be used, even if code elsewhere caches a reference
+to one of the translation functions. If you're curious, check out
+Django's source code [1].
+
+[0] https://docs.python.org/2.7/library/gettext.html#the-gnutranslations-class
+[1] https://github.com/django/django/blob/1.4.8/django/utils/translation/__init__.py#L66
+"""
+from django.utils.translation import _trans as translation
+
+import monkey_patch
+
+ATTRIBUTES = [
+    'gettext',
+    'ugettext',
+]
+
+
+def is_patched():
+    """
+    Check if the translation module has been monkey-patched
+    """
+    patched = True
+    for attribute in ATTRIBUTES:
+        if not monkey_patch.is_patched(translation, attribute):
+            patched = False
+            break
+    return patched
+
+
+def patch():
+    """
+    Monkey-patch the translation functions
+
+    Affected Methods:
+        - gettext
+        - ugettext
+    """
+    def decorate(function, message_default=u''):
+        """
+        Decorate a translation function
+
+        Default message is a unicode string, but gettext overrides this
+        value to return a UTF8 string.
+        """
+        def dont_translate_empty_string(message):
+            """
+            Return the empty string when passed a falsey message
+            """
+            if message:
+                message = function(message)
+            else:
+                message = message_default
+            return message
+        return dont_translate_empty_string
+    gettext = decorate(translation.gettext, '')
+    ugettext = decorate(translation.ugettext)
+    monkey_patch.patch(translation, 'gettext', gettext)
+    monkey_patch.patch(translation, 'ugettext', ugettext)
+    return is_patched()
+
+
+def unpatch():
+    """
+    Un-monkey-patch the translation functions
+    """
+    was_patched = False
+    for name in ATTRIBUTES:
+        # was_patched must be the second half of the or-clause, to avoid
+        # short-circuiting the expression
+        was_patched = monkey_patch.unpatch(translation, name) or was_patched
+    return was_patched