fix for pypa/pip#9827 and CVE-2021-28363

tox.ini

@@ -36,6 +36,7 @@ setenv =
     mysql: DJANGO_EXTENSIONS_DATABASE_NAME = {env:DJANGO_EXTENSIONS_DATABASE_NAME:django_extensions_test}
 
 deps =
+    pip >= 21.1
     -rrequirements-dev.txt
     dj22: Django==2.2
     dj30: Django>=3.0,<3.1
@@ -47,38 +48,45 @@ deps =
 
 [testenv:precommit]
 deps =
+    pip >= 21.1
     pre-commit
 commands = pre-commit run -a
 
 [testenv:safety]
 deps =
+    pip >= 21.1
     safety
 commands = safety check --full-report
 
 [testenv:mypy]
 deps =
+    pip >= 21.1
     mypy
 commands = mypy --ignore-missing-imports django_extensions
 
 [testenv:compile-catalog]
 whitelist_externals =
     make
 deps =
+    pip >= 21.1
     Babel
 commands =
     make compile-catalog
 
 [testenv:py37-flake8]
 deps =
+    pip >= 21.1
     flake8
 commands = flake8 django_extensions tests
 
 [testenv:py38-flake8]
 deps =
+    pip >= 21.1
     flake8
 commands = flake8 django_extensions tests
 
 [testenv:py39-flake8]
 deps =
+    pip >= 21.1
     flake8
 commands = flake8 django_extensions tests