copr-fe: catch exceptions while checking uptime robot

roles/copr/frontend/templates/copr-cdn-check.py.j2

@@ -1,8 +1,40 @@
 #! /usr/bin/python3
 
+"""
+Ask UptimeRobot service how the CDN works.
+
+The API output looks like:
+
+{
+  "stat": "ok",
+  "pagination": {
+    "offset": 0,
+    "limit": 50,
+    "total": 1
+  },
+  "monitors": [
+    {
+      "id": 788475080,
+      "friendly_name": "Copr's CDN",
+      "url": "https://download.copr.fedorainfracloud.org/",
+      "type": 1,
+      "sub_type": "",
+      "keyword_type": null,
+      "keyword_case_type": 0,
+      "keyword_value": "",
+      "port": "",
+      "interval": 600,
+      "timeout": 30,
+      "status": 2,
+      "create_datetime": 1624272619
+    }
+  ]
+}
+"""
+
+import logging
 import sys
 import requests
-import logging
 
 # NAGIOS exit codes
 NAG_UNKNOWN = 3
@@ -93,5 +125,9 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except Exception as exc:
+        LOG.exception("some exception occured: %s", exc)
+
     sys.exit(NAG_UNKNOWN)