Update pytest

requirements.txt

@@ -9,10 +9,10 @@ django_polymorphic==2.1.2
 django-rest-polymorphic==0.1.8
 mysqlclient==2.0.1
 PyJWT==1.7.1
-pytest==6.0.1
-pytest-django==3.9.0
-coverage==5.2.1
+pytest==6.1.1
+pytest-django==4.0.0
+coverage==5.3
 ipython==7.16.1
 mixer==6.1.3
-pytest-mock==3.2.0
-pytest-cov==2.10.0
+pytest-mock==3.3.1
+pytest-cov==2.10.1