Bug#852908: mako: FTBFS: Test failures

[Piotr Ożarowski]

> The failure is caused by the recent upload of pygments 2.2.0. With this new
> release the 'u' prefix is omitted from the rendered utf8 strings, as in:
>  <span class="s1">&#39;&#x43F;&#x440;&#x438;&#x432;&#x435;&#x442;&#39;</span>
> while pygments 2.1.3 gives:
>  <span class="s1">u&#39;&#x43F;&#x440;&#x438;&#x432;&#x435;&#x442;&#39;</span>

hmmm... that's weird as my first thought was it was due to new pygnents
so I tested it with old one and it failed as well... I probably messed
it somehow. Thanks for the patch!