BOM-1404 Updated tox settings (#23439)

Issue: https://openedx.atlassian.net/browse/BOM-1404



* Fixed Django 2.x installation process in tox
* Updated xdist worker Django installation code
* Use correct tox environment variable name

Co-authored-by: Jeremy Bowman <jbowman@edx.org>

requirements/edx/django20.txt

+Django>=2.0,<2.1
+git+https://github.com/jazzband/django-oauth-toolkit.git@bf1525e85a06929016b1fe35d863e62e58124a2f#egg=oauth2_provider
+

requirements/edx/django21.txt

+Django>=2.1,<2.2
+git+https://github.com/jazzband/django-oauth-toolkit.git@bf1525e85a06929016b1fe35d863e62e58124a2f#egg=oauth2_provider
+

requirements/edx/django22.txt

+Django>=2.2,<3.0
+git+https://github.com/jazzband/django-oauth-toolkit.git@bf1525e85a06929016b1fe35d863e62e58124a2f#egg=oauth2_provider
+

scripts/xdist/prepare_xdist_nodes.sh

@@ -11,10 +11,14 @@ python scripts/xdist/pytest_worker_manager.py -a up -n ${XDIST_NUM_WORKERS} \
 -iam ${XDIST_WORKER_IAM_PROFILE_ARN}
 
 # Install the correct version of Django depending on which tox environment (if any) is in use
-if [[ -z ${TOX_ENV+x} ]] || [[ ${TOX_ENV} == 'null' ]]; then
+if [[ -z ${TOXENV+x} ]] || [[ ${TOXENV} == 'null' ]]; then
     DJANGO_REQUIREMENT="-r requirements/edx/django.txt"
-else
-    DJANGO_REQUIREMENT=$(pip freeze | grep "^[Dd]jango==")
+elif [[ ${TOXENV} == *'django20'* ]]; then
+    DJANGO_REQUIREMENT="-r requirements/edx/django20.txt"
+elif [[ ${TOXENV} == *'django21'* ]]; then
+    DJANGO_REQUIREMENT="-r requirements/edx/django21.txt"
+elif [[ ${TOXENV} == *'django22'* ]]; then
+    DJANGO_REQUIREMENT="-r requirements/edx/django22.txt"
 fi
 
 ip_list=$(<pytest_worker_ips.txt)

tox.ini

@@ -69,9 +69,9 @@ passenv =
 
 deps =
     django111: -r requirements/edx/django.txt
-    django20: Django>=2.0,<2.1
-    django21: Django>=2.1,<2.2
-    django20,django21: git+https://github.com/jazzband/django-oauth-toolkit.git@bf1525e85a06929016b1fe35d863e62e58124a2f#egg=oauth2_provider
+    django20: -r requirements/edx/django20.txt
+    django21: -r requirements/edx/django21.txt
+    django22: -r requirements/edx/django22.txt
     -r requirements/edx/testing.txt
 whitelist_externals =
     /bin/bash