Merge pull request pandas-dev#680 from shashank88/pytest_cov_update

Upgrade pytest-cov to > 2.6.1 to fix man-group/arctic#678

Author: shashank88

setup.py

@@ -92,8 +92,8 @@ def run_tests(self):
                      ],
     tests_require=["mock",
                    "mockextras",
-                   "pytest<4.1",
-                   "pytest-cov",
+                   "pytest",
+                   "pytest-cov>=2.6.1",
                    "pytest-server-fixtures",
                    "pytest-timeout",
                    "pytest-xdist",