          if len(auth) == 1:
              msg = 'Invalid basic header. No credentials provided.'
              raise exceptions.AuthenticationFailed(msg)
          elif len(auth) > 2:
              msg = 'Invalid basic header. Credentials string should not contain spaces.'
              raise exceptions.AuthenticationFailed(msg)
  
          try:
              auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
          except (TypeError, UnicodeDecodeError):
 
</s> remove             msg = 'Invalid basic header. No credentials provided.'
 </s> add             msg = _("Invalid basic header. No credentials provided.") </s> remove             msg = 'Invalid token header. Token string should not contain spaces.'
 </s> add             msg = _("Invalid token header. Token string should not contain spaces.") </s> remove             msg = 'Invalid token header. No credentials provided.'
 </s> add             msg = _("Invalid token header. No credentials provided.") </s> remove             msg = 'Invalid basic header. Credentials not correctly base64 encoded'
 </s> add             msg = _("Invalid basic header. Credentials not correctly base64 encoded.") </s> remove                 msg = _('Unable to log in with provided credentials.')
 </s> add                 msg = _("Unable to log in with provided credentials.")
            msg = _("Invalid basic header. Credentials string should not contain spaces.")
          if len(auth) == 1:
              msg = 'Invalid basic header. No credentials provided.'
              raise exceptions.AuthenticationFailed(msg)
          elif len(auth) > 2:
            msg = _("Invalid basic header. Credentials string should not contain spaces.")
              raise exceptions.AuthenticationFailed(msg)
  
          try:
              auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
          except (TypeError, UnicodeDecodeError):
keep keep keep keep replace keep keep keep keep keep
 use double quotes for user visible strings; end user visible strings in full stops; add some missing translation tags 
rest_framework/authentication.py