pytype: add Python type annotations where necessary to guide pytype

Mute pytype warnings:

File "kallithea/lib/auth.py", line 142, in _cached_perms_data: No attribute 'DEFAULT_USER_ID' on module 'kallithea' [module-attr]
File "kallithea/lib/vcs/backends/base.py", line 73, in ...: No attribute '...' on BaseRepository [attribute-error]
File "kallithea/lib/vcs/backends/base.py", line 405, in ...: No attribute '...' on BaseChangeset [attribute-error]
File "kallithea/tests/api/api_base.py", line 2397, in test_api_get_changeset: No attribute 'TEST_REVISION' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2445, in test_api_get_pullrequest: No attribute 'TEST_PR_DST' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2445, in test_api_get_pullrequest: No attribute 'TEST_PR_SRC' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2467, in test_api_get_pullrequest: No attribute 'TEST_PR_REVISIONS' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 67, in api_call: No attribute 'app' on _BaseTestApi [attribute-error]
File "kallithea/tests/base.py", line 154, in log_user: No attribute 'app' on TestController [attribute-error]
File "kallithea/tests/base.py", line 169, in _get_logged_user: No attribute '_logged_username' on TestController [attribute-error]

imports: try to use global imports unless it is a layering violation

To minimize the impact, do imports that violate the layering at runtime instead
of at import time.

py3: add b'' annotations in some places where they will be needed later

Mostly entirely trivial adding of b prefix that is a ignored for py2 ... and
also a bit of related trivial reformatting/refactorings.

scm: don't try to get IP address from web request in model

Remove a layering violation and make functions more reusable when they no
longer depend on global state.

At this level, the IP address (and information about the current user) is only
used for hooks logging push / pull operations. Arguably, IP address logging
only belongs in an HTTP access log, not in the log of push/pull operations. But
as long as we have IP addresses in the logs, we have to provide it. The (good?)
alternative would be to drop IP address from the push / pull logs ...

tests: prepare for adding CSRF protection on login forms

CSRF is about avoiding abuse of credentials by doing things in existing
sessions. The login form does not have any previous credentials, so there is
nothing to abuse and no real need for CSRF protection. But there is still an
unauth session, so we *can* have CSRF protection.

CSRF protection is currently in LoginRequired (which obviously isn't
applied to the login form), but let's prepare for changing that.

tests: remove tests of UI notifications

This commit is part of the removal of the UI notification feature from
Kallithea, which is not deemed useful in its current form. Only email
notifications are preserved.

tests: Remove metaprogramming constructs for vcs test classes (issue #309):

- Removed use of the globals() and type() constructs to
programatically instantiate Git/Mercurial-specific test
classes. This should make it a bit clearer what tests are being run
at the expense of possible future VCS additions.
- Removed the SCM_TESTS VCS test configuration variable, since it got
removed. Previously it was used for instantiating test classes.
- Updated small snippet of inline documentation that described the use
of SCM_TESTS variable. New text points to inheriting from generic
test classes instead.
- base.py had a dead snippet - kill it.

codingstyle: trivial whitespace fixes

Reported by flake8.

tests: put all temporary files in one top directory

Use KALLITHEA_TESTS_TMP_PATH or a create a temporary /tmp/kallithea-test-*
directory.

Some temporary files might still be placed in /tmp ... but nothing should be
left behind.

tests: drop 'environ' as global variable - just pass it to URLGenerator as temporary variable

HTTP_HOST is mandatory - specify it as 'example.com'.

Add JSON-RPC API for reading changeset status

Allows reading a changeset status as json. This is useful for e.g. reporting,
extracting review status for all changesets between two releases.

tests: move time zone setup to pytest_configure

Test setup stuff belongs in pytest_configure.

backend: replace Pylons with TurboGears2

Replace the no-longer-supported Pylons application framework by TurboGears2
which is largely compatible/similar to Pylons.
Some interesting history is described at:
https://en.wikipedia.org/wiki/TurboGears

Changes by Dominik Ruf:
- fix sql config in test.ini

Changes by Thomas De Schampheleire:
- set-up of test suite
- tests: 'fix' repo archival test failure
Between Pylons and TurboGears2, there seems to be a small difference in the
headers sent for repository archive files, related to character encoding.
It is assumed that this difference is not important, and that the test
should just align with reality.
- remove need to import helpers/app_globals in lib
TurboGears2 by default expects helpers and app_globals to be available
in lib. For this reason kallithea/lib/__init__.py was originally changed
to include those files. However, this triggered several types of
circular import problems. If module A imported something from lib (e.g.
lib.annotate), and lib.helpers imported (possibly indirectly) module A,
then there was a circular import. Fix this by overruling the relevant
method of tg AppConfig, which is also hinted in the TurboGears2 code.
Hereby, the include of something from lib does not automatically import
helpers, greatly reducing the chances of circular import problems.
- make sure HTTP error '400' uses the custom error pages
TurboGears2 does not by default handle HTTP status code
'400 (Bad Request)' via the custom error page handling, causing a
standard non-styled error page.
- disable transaction manager
Kallithea currently handles its own transactions and does not need the
TurboGears2 transaction manager. However, TurboGears2 tries to enable it
by default and fails, throwing an error during application initialization.
The error itself seemed to be harmless for normal application functioning,
but was nevertheless confusing.
- add backlash as required dependency: backlash is meant as the WebError
replacement in TurboGears2 (originally WebError is part of Pylons). When
debug==true, it provides an interactive debugger in the browser. When
debug==false, backlash is necessary to show backtraces on the console.
- misc fixes

tg: minimize future diff by some mocking and replacing some pylons imports with tg

No actual tg dependency yet, just a temporary hack faking tg as an alias for
pylons.

Based on work by Alessandro Molina.

tests: remove intermediate init_stack method

Grafted and modified by Mads Kiilerich.

Turbogears2 migration: replace pylons.url by kallithea.config.routing.url

In preparation for the migration to Turbogears2, introduce a
kallithea.config.routing.url to replace pylons.url. The implementation is
basically the same: wrap around routes.url().

This change involves:
- a number of import statement changes
- fixing some tests in test_libs.py; to avoid duplication, the different
implementations of fake_url were grouped in one place.

This change was first proposed by Alessandro Molina in his initial
port. Following changes were made afterwards:
- move UrlGenerator from kallithea.lib.utils to kallithea.config.routing
- add documentation to UrlGenerator
- kallithea/lib/auth.py used url_for instead of url, for no apparent reason
so this was changed.
- fix libs tests
- rebase onto Pylons-based Kallithea first

tests: add as little code as possible in __init__.py

kallithea/tests/__init__.py contained quite a lot of code, including the test
base class TestController. This in itself may be considered bad practice.

Specifically, this poses a problem when using pytest 3.0+, in which asserts
in some files are not automatically rewritten to give improved assert
output. That problem can be fixed by explicitly registering such files for
assertion rewriting, but that register call should be executed _before_ said
files are imported. I.e. if the register call is in
kallithea/tests/__init__.py, assert calls in __init__.py itself can not be
rewritten.

Since the TestController base class does effectively contain asserts, and we
do not want to execute the register call from somewhere outside the
kallithea/tests directory, we need to move the TestController class to
another file (kallithea/tests/base.py) so we can have a register call in
__init__.py before loading base.py.

While not strictly necessary to fix the mentioned pytest problem, we take
the opportunity to fully clean __init__.py and move everything to
the new kallithea/tests/base.py. While doing so, unnecessary imports are
removed, and imports are ordered alphabetically. Explicit imports of symbols
from modules that were already imported as a whole, are removed in favor of
fully qualifying the references (e.g. tempfile._RandomNameSequence).