Bump pytest-black from 0.3.9 to 0.3.10 (#456)

Author: dependabot[bot]

requirements/requirements_dev.txt

@@ -11,7 +11,7 @@ placebo==0.9.0
 pre-commit==2.6.0
 pylint==2.5.3
 pytest==5.4.3
-pytest-black==0.3.9
+pytest-black==0.3.10
 pytest-cov==2.10.0
 pytest-datadir==1.3.1
 pytest-flake8==1.0.6