Refactor clone with timout util from hg loader

This will be also used by the new bzr loader. A separate patch will refactor this in the hg loader.

---

Migrated from D6984 (view on Phabricator)

swh/loader/mercurial/tests/test_hgutil.py

-# Copyright (C) 2020-2021  The Software Heritage developers
-# See the AUTHORS file at the top-level directory of this distribution
-# License: GNU General Public License version 3, or any later version
-# See top-level LICENSE file for more information
-import signal
-import time
-import traceback
-
-from mercurial import hg  # type: ignore
-import pytest
-
-from .. import hgutil
-
-
-def test_clone_timeout(monkeypatch):
-    src = "https://www.mercurial-scm.org/repo/hello"
-    dest = "/dev/null"
-    timeout = 1
-    sleepy_time = 100 * timeout
-    assert sleepy_time > timeout
-
-    def clone(*args, **kwargs):
-        # ignore SIGTERM to force sigkill
-        signal.signal(signal.SIGTERM, lambda signum, frame: None)
-        time.sleep(sleepy_time)  # we make sure we exceed the timeout
-
-    monkeypatch.setattr(hg, "clone", clone)
-
-    with pytest.raises(hgutil.CloneTimeout) as e:
-        hgutil.clone(src, dest, timeout)
-    killed = True
-    assert e.value.args == (src, timeout, killed)
-
-
-def test_clone_error(caplog, tmp_path, monkeypatch):
-    src = "https://www.mercurial-scm.org/repo/hello"
-    dest = "/dev/null"
-    expected_traceback = "Some traceback"
-
-    def clone(*args, **kwargs):
-        raise ValueError()
-
-    def print_exc(file):
-        file.write(expected_traceback)
-
-    monkeypatch.setattr(hg, "clone", clone)
-    monkeypatch.setattr(traceback, "print_exc", print_exc)
-
-    with pytest.raises(hgutil.CloneFailure) as e:
-        hgutil.clone(src, dest, 1)
-    assert e.value.args == (src, dest, expected_traceback)