Fix flask run by not monkey patching for gevent in wsgi.py (CTFd#1101)

* Fixes `flask run` debug server by not monkey patching in `wsgi.py`
* Closes CTFd#1099

Author: ColdHeat

wsgi.py

@@ -1,8 +1,14 @@
-from gevent import monkey
-monkey.patch_all()
+import os
+
+# Detect if we're running via `flask run` and don't monkey patch
+if not os.getenv("FLASK_RUN_FROM_CLI"):
+    from gevent import monkey
+
+    monkey.patch_all()
+
 from CTFd import create_app
 
 app = create_app()
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     app.run(debug=True, threaded=True, host="127.0.0.1", port=4000)