#184: Add file specific ignore for 'random' usage

- S311 (from Bandit) states "Standard pseudo-random generators are not suitable for security/cryptographic purposes.". The generator script doesn't generate data that would be vulnerable to security (no keys or anything of that nature is created using the random library) hence this status code is ignored

.flake8

@@ -6,5 +6,5 @@ max-complexity = 10
 max-line-length = 80
 application-import-names = datagateway_api,test,util
 import-order-style = google
-per-file-ignores = test/*:S101
+per-file-ignores = test/*:S101,util/icat_db_generator.py:S311
 enable-extensions=G