[PATCH v3] tests: fix assertion rewriting in some tests with pytest-3.0.0+

[Thomas De Schampheleire]

# HG changeset patch
# User Thomas De Schampheleire <thomas.de.schampheleire at gmail.com>
# Date 1473428048 -7200
#      Fri Sep 09 15:34:08 2016 +0200
# Node ID 98d44af325f0504b1219ab8158383b40bd4a0a34
# Parent  59639343672495cb89be54b98f1d6d3a4c44307c
tests: fix assertion rewriting in some tests with pytest-3.0.0+

Since pytest 3.0.0, asserts present in modules that are not directly seen by
pytest as 'test modules', are no longer rewritten to have improved
reporting, unless they are explicitly marked as up-for-rewriting.
Rationale from pytest upstream:

    However since we do not want to test different bytecode then you will
    run in production this hook only re-writes test modules themselves as
    well as any modules which are part of plugins. Any other imported module
    will not be re-written and normal assertion behaviour will happen.

This is e.g. the case for asserts in files like
kallithea/tests/api/api_base.py and kallithea/tests/models/common.py.

See
http://doc.pytest.org/en/latest/changelog.html#id13
http://doc.pytest.org/en/latest/writing_plugins.html#assertion-rewriting

This commit registers all modules below kallithea.tests for assert
rewriting, but note that asserts in kallithea/tests/__init__.py itself are
not rewritten as kallithea.tests is already imported when the register
statement is encountered.
Moving the register statement to kallithea/__init__.py would fix that, but
even then asserts in kallithea/tests/__init__.py seem not to be rewritten
(let alone the issue that we do not want a pytest dependency enforced in
kallithea/__init__.py which is also used in production).
Moving out some of the code from kallithea/tests/__init__.py to a proper
module, as suggested by Mads Kiilerich, is assumed to solve that problem.

diff --git a/kallithea/__init__.py b/kallithea/__init__.py
--- a/kallithea/__init__.py
+++ b/kallithea/__init__.py
@@ -86,3 +86,8 @@ if len(VERSION) > 3:
 import uuid
 if not hasattr(uuid, '_uuid_generate_random'):
     uuid._uuid_generate_random = None
+
+# make sure that all asserts under kallithea/tests benefit from advanced assert
+# reporting, before importing these modules.
+import pytest
+pytest.register_assert_rewrite('kallithea.tests.')