make sure that random slugs are unique (#454)

* make sure that random slugs are unique

* prevent busy-looping

Author: marten-seemann

interop.py

@@ -1,7 +1,7 @@
 import json
 import logging
 import os
-from random_slugs import generate_slug
+from unique_random_slugs import generate_slug
 import re
 import shutil
 import statistics

testcases.py

@@ -3,7 +3,7 @@
 import logging
 import os
 import random
-from random_slugs import generate_slug
+from unique_random_slugs import generate_slug
 import re
 import shutil
 import string

unique_random_slugs.py

@@ -0,0 +1,12 @@
+from random_slugs import generate_slug as original_generate_slug
+
+_used_slugs = set()
+
+
+def generate_slug():
+    for _ in range(100000):
+        slug = original_generate_slug()
+        if slug not in _used_slugs:
+            _used_slugs.add(slug)
+            return slug
+    raise ValueError("Unable to generate unique slug after 100k attempts")