Migrations up-to-date check no longer requires Redis

Avoid relying on Redis for up-to-date checks of
applied DB migrations by instead inspecting the
results of the 'showmigrations' listing command
and checking for the presence of the unchecked
checkbox ASCII representation '[ ]'.

This change makes the DB migration status check
more self-contained and less fragile.

ixc_django_docker/bin/migrate.sh

@@ -21,30 +21,35 @@ if [[ DJANGO_VERSION_LESS_THAN_1_7 == 'True' ]]; then
 fi
 
 if [[ DJANGO_VERSION_LESS_THAN_1_10 == 'True' ]]; then
-    manage.py migrate --list > "$DIR/migrate.txt"
+    manage.py migrate --list > "$DIR/migrate.txt" 2>/dev/null
 else
-    manage.py showmigrations > "$DIR/migrate.txt"
+    manage.py showmigrations > "$DIR/migrate.txt" 2>/dev/null
 fi
 
-# Is local listing of migrations the same as one cached in Redis
-# (i.e. as has already been completed and cached by another server instance)?
-if ! redis-cache.py -v -x match ixc-django-docker:migrate-list < "$DIR/migrate.txt"; then
-	echo 'Migrations are out of date.'
+# Rely on the formatted text output of Django's migration listing to tell us
+# whether there are any pending migrations, which are flagged with an empty
+# ASCII checkbox versus a checked one. Grep for the unapplied migration '[ ]'
+# text as a flag for when migrations need to be applied, and when grep returns
+# an **error** status we know there are **no unapplied migrations**
+#
+# Here is an example of the output of 'showmigrations' etc:
+#
+#     wagtailusers
+#      [X] 0001_initial
+#      [ ] 0002_add_verbose_name_on_userprofile
+set +e
+grep '\[ \]' "$DIR/migrate.txt" > /dev/null
+HAS_ALL_MIGRATIONS_APPLIED=$?
+set -e
+
+if [[ HAS_ALL_MIGRATIONS_APPLIED -ne 0 ]]; then
+	echo 'Migrations are up-to-date - no migration listing items contain "[ ]"'
+else
+    echo 'Migrations are out of date - one or more migration listing items contain "[ ]"'
 
-	# Skip initial migration if all tables created by the initial migration
-	# already exist.
-	if [[ $(python -c 'import django; print(django.get_version());') < 1.7 ]]; then
+	if [[ DJANGO_VERSION_LESS_THAN_1_7 == 'True' ]]; then
 		manage.py migrate --noinput  # South has no `--fake-initial` option
 	else
 		manage.py migrate --fake-initial --noinput
 	fi
-
-    if [[ DJANGO_VERSION_LESS_THAN_1_10 == 'True' ]]; then
-        manage.py migrate --list > "$DIR/migrate.txt"
-    else
-        manage.py showmigrations > "$DIR/migrate.txt"
-    fi
-
-	# Cache listing of up-to-date migrations
-	redis-cache.py -vv -x set ixc-django-docker:migrate-list < "$DIR/migrate.txt"
 fi