Use pytest-cov with tox, for coverage

setup.py

@@ -145,6 +145,7 @@ extras = {
         'mock',                         # 1.0.1
         'nose',                         # 1.3.0
         'pytest',                       # 4.6.11
+        'pytest-cov',                   # 2.12.1
     ],
 }
 

tox.ini

@@ -22,7 +22,7 @@ deps = invoke
 commands =
         pip install --upgrade pip
         pip install --upgrade --upgrade-strategy eager rattail[auth,bouncer,db,tests] appy luigi xlrd
-        nosetests {posargs:--with-coverage --cover-html-dir={envtmpdir}/coverage}
+        pytest --cov=rattail --cov-report=html
 
 [testenv:docs]
 basepython = python3