Add a dedicated "lpimport" tox testenv

To simplify the launchpadlib dependency installation for the
storyboard-migrate utility, use a separate tox testenv specifically
for this purpose and put that as its only additional runtime
requirement. Name the testenv "lpimport" with the expectation that
in time we may also rename the storyboard-migrate utility similarly
(so as to disambiguate it from the Alembic migrations we rely on
for database schema upgrades).

Change-Id: I8bd36bf69c235c8957ae4a161fd22cbe80028cf4

doc/source/migration.rst

@@ -79,7 +79,7 @@ Test Migration
 
    You can do this with the following command::
 
-    tox -e venv -- storyboard-migrate
+    tox -e lpimport --
       --config-file etc/storyboard.conf
       --from-project $PROJECT_IN_LAUNCHPAD
       --to-project $PROJECT_IN_STORYBOARD
@@ -89,7 +89,7 @@ Test Migration
    `$PROJECT_IN_STORYBOARD` should be replaced the name of the project
    you are importing into in StoryBoard, for example `openstack/monasca`.
 
-   Two parameters of the `storyboard-migrate` command
+   Two parameters of the `storyboard-migrate` command used by `lpimport`
    allows for filtering by the tags associated to the bug.
    Both parameters accept a comma-separated lists of tags
    and they are mutually exclusive.

requirements.txt

@@ -29,6 +29,5 @@ apscheduler>=3.0.1,<3.1.0
 python_dateutil>=2.4.0
 oslo.concurrency>=3.8.0         # Apache-2.0
 oslo.i18n>=2.1.0  # Apache-2.0
-#launchpadlib         # Only for migration
 python-swiftclient
-openstacksdk
+openstacksdk

tox.ini

@@ -72,5 +72,12 @@ basepython = python3
 deps = bindep
 commands = bindep test
 
+[testenv:lpimport]
+basepython = python3
+# The Launchpad bug import tool uses launchpadlib, which is not a typical
+# runtime dependency of anything else in StoryBoard
+deps = launchpadlib
+commands = storyboard-migrate {posargs}
+
 [hacking]
 import_exceptions = storyboard._i18n