doc: Update instructions to use supported versions of Python (Fixes #1510) (#1515)

* Fixes #1510

Author: DangerChamp

test/README.md

@@ -43,21 +43,21 @@ the test for vendor_package_pairs:
 
 ## Running tests on different versions of Python
 
-Our CI currently runs tests on Python 3.6 and 3.7 under Linux.
+Our CI currently runs tests on Python 3.7 - 3.10 under Linux.
 
 The recommended way to do this yourself is to use python's `virtualenv`
 
 You can set up virtualenv for all these environments:
 
 ```console
-virtualenv -p python3.6 venv3.6
-virtualenv -p python3.7 venv3.7
+virtualenv -p python3.8 venv3.8
+virtualenv -p python3.9 venv3.9
 ```
 
-To activate one of these (the example uses 3.6), run the tests, and deactivate:
+To activate one of these (the example uses 3.8), run the tests, and deactivate:
 
 ```console
-source venv3.6/bin/activate
+source venv3.8/bin/activate
 python setup.py test
 deactivate
 
@@ -145,5 +145,3 @@ pytest -v test/test_checkers.py -k python
 ```
 
 ## Known issues
-
-If you're using Windows we **strongly** recommend also `pdftotext`. We experienced problems running tests without this. The best approach to do this is through [conda](https://docs.conda.io/projects/conda/en/latest/user-guide/install/windows.html) (click [here](https://anaconda.org/conda-forge/pdftotext) to find out how to install this package with conda).