Update pyupgrade to use Python >= 3.9 syntax and functionality.

Author: Kami

tox.ini

@@ -367,13 +367,13 @@ commands =
 deps =
     -r{toxinidir}/requirements-lint.txt
 commands =
-    bash -c "find libcloud/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find contrib/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find demos/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find pylint_plugins/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find integration/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find scripts/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
-    bash -c "find docs/examples/ -name '*.py' -print0 | xargs -0 pyupgrade --py37-plus --py3-only"
+    bash -c "find libcloud/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find contrib/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find demos/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find pylint_plugins/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find integration/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find scripts/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
+    bash -c "find docs/examples/ -name '*.py' -print0 | xargs -0 pyupgrade --py39-plus --py3-only"
 
     isort {toxinidir}