Improve integration tests scripts (#316)

When running locally, they would generate a symbolic link inside the
dags symbolic link, if it previously existed.

This PR solves these limitations.

scripts/test/integration-setup.sh

@@ -4,6 +4,15 @@ set -v
 set -x
 set -e
 
+if [ -L "dags" ]; then
+    echo "Symbolic link 'dags' already exists."
+elif [ -e "dags" ]; then
+    echo "'dags' exists but is not a symbolic link. Please resolve this manually."
+else
+    ln -s dev/dags dags
+    echo "Symbolic link 'dags' created successfully."
+fi
+
 rm -rf airflow.*
 pip freeze | grep airflow
 airflow db reset -y

scripts/test/integration.sh

@@ -10,8 +10,6 @@ ls $AIRFLOW_HOME
 
 airflow db check
 
-ln -s dev/dags dags
-
 pytest -vv \
     --cov=dagfactory \
     --cov-report=term-missing \