Bug#762933: debsources: webapp should not require python-matplotlib

[Clément Schreiner <clement@mux.me>]

On Fri, 26 Sep 2014 14:30:53 +0200 Stefano Zacchiroli <zack@debian.org> wrote:
> Since the refactoring with the top-level debsources/ module, the webapp
> requires python-matplotlib to be installed to run properly. That is
> unfortunate, as matplotlib is needed only by the updater, and induces weird
> requirements on the webserver user (e.g., a writable /var/www/.matplotlib ?!!).
> 
> We should track down and remove this dependency.

The dependency comes from debsources.mainlib, which imports
debsources.updater, which imports debsources.charts.

However, in debsources.updater, only the function 'update_charts'
requires debsources.charts.

Moving the 'from debsources import charts' from the top of updater.py to
the top of the 'update_charts' function fixes the problem. A patch is
attached.

This should break PEP8 compliance[1] but flake8 doesn't complain after
applying my changes. The unit tests run fine too.

Maybe this patch is not ideal: from debsources.updater,
debsources.mainlib only requires the functions 'parse_stages' and
'pp_stage' as well as the constants UPDATE_STAGES, KNOWN_STAGES and
NO_OBSERVERS. A better fix might be to move those somewhere else
(updater_utils.py?).

Any thoughts?


[1] [https://www.python.org/dev/peps/pep-0008/#imports]

>From 74d6f1560fdaadcff3960d68e4d094a7f3a9c827 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Schreiner?= <clement@mux.me>
Date: Tue, 24 Mar 2015 14:06:26 +0100
Subject: [PATCH] Import matploblib in update_charts only.

---
 debsources/updater.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/debsources/updater.py b/debsources/updater.py
index 0c90826..d0cc389 100644
--- a/debsources/updater.py
+++ b/debsources/updater.py
@@ -31,7 +31,6 @@ from datetime import datetime
 from email.utils import formatdate
 from sqlalchemy import sql, not_
 
-from debsources import charts
 from debsources import db_storage
 from debsources import fs_storage
 from debsources import statistics
@@ -510,6 +509,7 @@ def update_metadata(status, conf, session):
 def update_charts(status, conf, session, suites=None):
     """update stage: rebuild charts"""
 
+    from debsources import charts
     logging.info('update charts...')
     ensure_stats_dir(conf)
     suites = __target_suites(session, suites)
-- 
2.1.4