Comment 3 for bug 1745935

When setup package for nova, it will also install the package from test-requirements.txt which has whereto (“whereto>=0.3.0 # Apache-2.0”);
2018-01-29 04:19:41.019 | +inc/python:_setup_package_with_constraints_edit:558 ^[[m^[(B /opt/stack/requirements/.venv/bin/edit-constraints /opt/stack/requirements/upper-constraints.txt -- nova '-e file:///opt/stack/nova#egg=nova'
2018-01-29 04:19:43.115 | +inc/python:pip_install:359 ^[[m^[(B sudo -H http_proxy= https_proxy= no_proxy= PIP_FIND_LINKS= SETUPTOOLS_SYS_PATH_TECHNIQUE=rewrite /usr/local/bin/pip2.7 install -c /opt/stack/requirements/upper-constraints.txt -r /opt/stack/nova/test-requirements.txt -e /opt/stack/nova

https://github.com/openstack-dev/devstack/blob/master/inc/python#L348

https://github.com/openstack/nova/blob/ec8b9a59c018c41bb18d0e712ad2868706ac9db7/test-requirements.txt#L40

And whereto requires python-pcre (http://git.openstack.org/cgit/openstack/whereto/tree/requirements.txt); but python-pcre depends on libpcre3-dev.