Suppress UserWarning when finding module specs (#2121)

Found when linting this code:
```
import setuptools
import pip
```

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/test_manager.py b/tests/test_manager.py
index 16f1be80..4f76d09c 100644
--- a/tests/test_manager.py
+++ b/tests/test_manager.py
@@ -7,6 +7,7 @@ import site
 import sys
 import time
 import unittest
+import warnings
 from collections.abc import Iterator
 from contextlib import contextmanager
 from unittest import mock
@@ -383,6 +384,15 @@ class AstroidManagerTest(
             self.manager.ast_from_module_name(None)
 
 
+class IsolatedAstroidManagerTest(resources.AstroidCacheSetupMixin, unittest.TestCase):
+    def test_no_user_warning(self):
+        mgr = manager.AstroidManager()
+        with warnings.catch_warnings():
+            warnings.filterwarnings("error", category=UserWarning)
+            mgr.ast_from_module_name("setuptools")
+            mgr.ast_from_module_name("pip")
+
+
 class BorgAstroidManagerTC(unittest.TestCase):
     def test_borg(self) -> None:
         """Test that the AstroidManager is really a borg, i.e. that two different