Update pytest from 5.2.0 to 5.2.1

requirements.txt

@@ -4,7 +4,7 @@ Flask-SQLAlchemy==2.4.1
 SQLAlchemy==1.3.9
 WTForms==2.2.1
 coverage==4.5.4
-pytest==5.2.0
+pytest==5.2.1
 Flask-Cors==3.0.8
 pytest-cov==2.7.1
 pytest-flask==0.15.0