Fix CI pipeline: Add missing dependencies for performance tests

- Add Pillow, prettytable, and pyLibravatar to performance test jobs
- Make performance_tests.py work without Django dependencies
- Add local implementations of generate_random_email and random_string
- Fix ModuleNotFoundError: No module named 'PIL' in CI environment
- Fix flake8 redefinition warning

This resolves the pipeline failure in performance_tests_dev job.

scripts/performance_tests.py

@@ -11,18 +11,39 @@ import sys
 import time
 import statistics
 import hashlib
+import random
+import string
 from typing import Dict, List, Any, Optional, Tuple
 
 # Add project root to path
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-# Import utilities
-from ivatar.utils import generate_random_email
 from libravatar import libravatar_url
 from urllib.parse import urlsplit
 from prettytable import PrettyTable
 
 
+def random_string(length=10):
+    """Return some random string with default length 10"""
+    return "".join(
+        random.SystemRandom().choice(string.ascii_lowercase + string.digits)
+        for _ in range(length)
+    )
+
+
+# Try to import Django utilities for local testing, fallback to local implementation
+try:
+    from ivatar.utils import generate_random_email
+except ImportError:
+    # Use local version for external testing
+    def generate_random_email():
+        """Generate a random email address using the same pattern as test_views.py"""
+        username = random_string()
+        domain = random_string()
+        tld = random_string(2)
+        return f"{username}@{domain}.{tld}"
+
+
 # Django setup - only for local testing
 def setup_django() -> None:
     """Setup Django for local testing"""