Merge pull request #118 from rethinkdb/dependabot/pip/mock-3.0.3

Bump mock from 2.0.0 to 3.0.3

Author: gabor-boros

requirements.txt

@@ -1,6 +1,6 @@
 async-generator==1.10; python_version>="3.6"
 codacy-coverage==1.3.11
-mock==2.0.0
+mock==3.0.3
 pytest-cov==2.7.1
 pytest-tornasync; python_version >= '3.5'
 pytest-trio==0.5.2; python_version>="3.6"