Prevent unit tests from sending emails

test/conftest.py

@@ -540,3 +540,9 @@ def responses():
         not_used = set(mocked_urls) - set(used_urls)
         if not_used:
             pytest.fail(f"Found unused responses mocks: {not_used}", pytrace=False)
+
+
+@pytest.fixture(autouse=True)
+def _no_mail(monkeypatch):
+    """Remove sending mails from all tests."""
+    monkeypatch.delattr("smtplib.SMTP")