add file exists check

check_cert_file_expiry.py

@@ -4,6 +4,7 @@ import subprocess
 import datetime
 import argparse
 import enum
+import os
 import sys
 from email.utils import parsedate_to_datetime
 
@@ -50,6 +51,11 @@ if __name__ == '__main__':
     message = "Plugin failed"
     perfdata = {}
 
+    if not os.path.isfile(args.file):
+        status = Status.UNKNOWN
+        message = "File not found"
+
+    else:
         try:
             expiry_date = get_expiry_date(args.file)