Update pytest from 4.3.1 to 4.4.0

Author: pyup-bot

requirements-dev.txt

@@ -11,7 +11,7 @@ ipdb==0.11
 motor==2.0.0
 pytest-cov==2.6.1
 pytest-sugar==0.9.2
-pytest==4.3.1
+pytest==4.4.0
 python-dateutil==2.8.0
 sqlalchemy==1.3.1
 trafaret==1.2.0