ping database with python instead of mysql client (#1862)

* Replaces `mysqladmin ping` with a custom script
* Closes #725

ping.py

@@ -0,0 +1,34 @@
+"""
+Script for checking that a database server is available.
+Essentially a cross-platform, database agnostic mysqladmin.
+"""
+import time
+
+from sqlalchemy import create_engine
+from sqlalchemy.engine.url import make_url
+
+from CTFd.config import Config
+
+url = make_url(Config.DATABASE_URL)
+
+# Ignore sqlite databases
+if url.drivername.startswith("sqlite"):
+    exit(0)
+
+# Null out the database so raw_connection doesnt error if it doesnt exist
+# CTFd will create the database if it doesnt exist
+url.database = None
+
+# Wait for the database server to be available
+engine = create_engine(url)
+print(f"Waiting for {url} to be ready")
+while True:
+    try:
+        engine.raw_connection()
+        break
+    except Exception:
+        print(".", end="", flush=True)
+        time.sleep(1)
+
+print(f"{url} is ready")
+time.sleep(1)