mock signal registration to prevent errors when running tests under pypy

test/unit/conftest.py

@@ -96,6 +96,12 @@ def run(self, *args, **kwargs):
         return self._run_command(*args, **kwargs)
 
 
+@pytest.fixture(scope="session", autouse=True)
+def mock_signal():
+    with mock.patch('signal.signal'):
+        yield
+
+
 @pytest.fixture
 def b2_cli(console_tool_class):
     cli_tester = ConsoleToolTester()