[doc] Add requirement for gettext and graphviz
When running the tutorial from scratch, I had errors because these
two packages were not installed.
Tests: unittest
Depends:
python3-cubicweb, cubicweb-ctl,
@builddeps@,
python3-pytest,
python3-flake8,
python3-psycopg2, postgresql, postgresql-plpython,
python3-ldap3, slapd, ldap-utils
Restrictions: allow-stderr, isolation-container
Tests: skeleton-packaging
Depends:
python3-cubicweb, cubicweb-ctl,
python3-pyramid, python3-wsgicors,
devscripts, equivs, lintian, autopkgtest
Restrictions: allow-stderr, needs-root