skip coverge percentage cheking in case of $SKIP_ALL_TESTS is 1

tox.ini

@@ -32,4 +32,7 @@ commands =
     coverage run --source gso --omit="gso/migrations/*" -m pytest {posargs}
     coverage xml
     coverage html
-    coverage report --fail-under 80
+    sh -c "if [ $SKIP_ALL_TESTS -eq 1 ]; then echo 'Skipping coverage report'; else coverage report --fail-under 80; fi"
+
+allowlist_externals =
+    sh
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