change one more occurence of 3.6 to 3.7 in README.md

README.md

@@ -105,7 +105,7 @@ transaction.commit()
 ```
 
 ## Running the tests
-* Create and activate a virtualenv with a Python version of at least 3.6
+* Create and activate a virtualenv with a Python version of at least 3.7
 * Install dependencies with `pip install -r requirements-dev-minimal.txt`
 * Run tests with `python -m unittest discover tests -t /`