fix: use django 2.2 makemigrations --check (ietf-tools#4351)

Author: rjsparks

.github/workflows/build.yml

@@ -130,10 +130,8 @@ jobs:
         ./ietf/manage.py check
         ./ietf/manage.py migrate
         echo "Validating migrations..."
-        MSG=$(ietf/manage.py makemigrations 2>&1)
-        if ! ( echo ${MSG} | grep -q "^No changes detected$") ; then
+        if ! ( ietf/manage.py makemigrations --dry-run --check --verbosity 3 ) ; then
           echo "Model changes without migrations found."
-          echo ${MSG}
           exit 1
         fi
         echo "Running tests..."

.github/workflows/ci-run-tests.yml

@@ -44,8 +44,7 @@ jobs:
         ./ietf/manage.py check
         ./ietf/manage.py migrate
         echo "Validating migrations..."
-        MSG=$(ietf/manage.py makemigrations 2>&1)
-        if ! ( echo ${MSG} | grep -q "^No changes detected$") ; then
+        if ! ( ietf/manage.py makemigrations --dry-run --check --verbosity 3 ) ; then
           echo "Model changes without migrations found."
           echo ${MSG}
           exit 1