Update pytest, pytest-mock and pytest-xdist (#37)

Author: grktsh

Pipfile.lock

@@ -30,10 +30,10 @@ format =
     pyrfc3339 ~= 1.1
     rfc3986 ~= 1.1
 test =
-    pytest >= 4.4, < 6
-    pytest-cov ~= 2.6
-    pytest-mock ~= 1.10
-    pytest-xdist ~= 1.28
+    pytest
+    pytest-cov
+    pytest-mock
+    pytest-xdist
     pyyaml ~= 5.1
 
 [options.packages.find]