[format.python] initial formatting of the python code

This patch was generated by black [1]::

    make format.python

[1] https://github.com/psf/black

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/metrics/models.py

@@ -58,7 +58,7 @@ class Histogram:
 
     @property
     def quartile_percentage(self):
-        ''' Quartile in percentage '''
+        '''Quartile in percentage'''
         with self._lock:
             if self._count > 0:
                 return [int(q * 100 / self._count) for q in self._quartiles]