Pin pyyaml to latest version 3.12

[pyup-bot]

This PR pins PyYAML to the latest release 3.12.

Changelog

3.10

-----------------

* Do not try to build LibYAML bindings on platforms other than CPython
(Thank to olt(at)bogosoft(dot)com).
* Clear cyclic references in the parser and the emitter
(Thank to kristjan(at)ccpgames(dot)com).
* Dropped support for Python 2.3 and 2.4.

3.09

-----------------

* Fixed an obscure scanner error not reported when there is
no line break at the end of the stream (Thank to Ingy).
* Fixed use of uninitialized memory when emitting anchors with
LibYAML bindings (Thank to cegner(at)yahoo-inc(dot)com).
* Fixed emitting incorrect BOM characters for UTF-16 (Thank to
Valentin Nechayev)
* Fixed the emitter for folded scalars not respecting the preferred
line width (Thank to Ingy).
* Fixed a subtle ordering issue with emitting '%TAG' directives
(Thank to Andrey Somov).
* Fixed performance regression with LibYAML bindings.

3.08

-----------------

* Python 3 support (Thank to Erick Tryzelaar).
* Use Cython instead of Pyrex to build LibYAML bindings.
* Refactored support for unicode and byte input/output streams.

3.07

-----------------

* The emitter learned to use an optional indentation indicator
for block scalar; thus scalars with leading whitespaces
could now be represented in a literal or folded style.
* The test suite is now included in the source distribution.
To run the tests, type 'python setup.py test'.
* Refactored the test suite: dropped unittest in favor of
a custom test appliance.
* Fixed the path resolver in CDumper.
* Forced an explicit document end indicator when there is
a possibility of parsing ambiguity.
* More setup.py improvements: the package should be usable
when any combination of setuptools, Pyrex and LibYAML
is installed.
* Windows binary packages are built against LibYAML-0.1.2.
* Minor typos and corrections (Thank to Ingy dot Net
and Andrey Somov).

3.06

-----------------

* setup.py checks whether LibYAML is installed and if so, builds
and installs LibYAML bindings.  To force or disable installation
of LibYAML bindings, use '--with-libyaml' or '--without-libyaml'
respectively.
* The source distribution includes compiled Pyrex sources so
building LibYAML bindings no longer requires Pyrex installed.
* 'yaml.load()' raises an exception if the input stream contains
more than one YAML document.
* Fixed exceptions produced by LibYAML bindings.
* Fixed a dot '.' character being recognized as !!float.
* Fixed Python 2.3 compatibility issue in constructing !!timestamp values.
* Windows binary packages are built against the LibYAML stable branch.
* Added attributes 'yaml.__version__' and  'yaml.__with_libyaml__'.

3.05

-----------------

* Windows binary packages were built with LibYAML trunk.
* Fixed a bug that prevent processing a live stream of YAML documents in
timely manner (Thanks edward(at)sweetbytes(dot)net).
* Fixed a bug when the path in add_path_resolver contains boolean values
(Thanks jstroud(at)mbi(dot)ucla(dot)edu).
* Fixed loss of microsecond precision in timestamps
(Thanks edemaine(at)mit(dot)edu).
* Fixed loading an empty YAML stream.
* Allowed immutable subclasses of YAMLObject.
* Made the encoding of the unicode->str conversion explicit so that
the conversion does not depend on the default Python encoding.
* Forced emitting float values in a YAML compatible form.

3.04

-----------------

* Include experimental LibYAML bindings.
* Fully support recursive structures.
* Sort dictionary keys.  Mapping node values are now represented
as lists of pairs instead of dictionaries.  No longer check
for duplicate mapping keys as it didn't work correctly anyway.
* Fix invalid output of single-quoted scalars in cases when a single
quote is not escaped when preceeded by whitespaces or line breaks.
* To make porting easier, rewrite Parser not using generators.
* Fix handling of unexpected block mapping values.
* Fix a bug in Representer.represent_object: copy_reg.dispatch_table
was not correctly handled.
* Fix a bug when a block scalar is incorrectly emitted in the simple
key context.
* Hold references to the objects being represented.
* Make Representer not try to guess !!pairs when a list is represented.
* Fix timestamp constructing and representing.
* Fix the 'N' plain scalar being incorrectly recognized as !!bool.

3.03

-----------------

* Fix Python 2.5 compatibility issues.
* Fix numerous bugs in the float handling.
* Fix scanning some ill-formed documents.
* Other minor fixes.

3.02

-----------------

* Fix win32 installer.  Apparently bdist_wininst does not work well
under Linux.
* Fix a bug in add_path_resolver.
* Add the yaml-highlight example.  Try to run on a color terminal:
`python yaml_hl.py <any_document.yaml`.

3.01

-----------------

* Initial release.  The version number reflects the codename
of the project (PyYAML 3000) and differenciates it from
the abandoned PyYaml module.

Links

• PyPI: https://pypi.org/project/pyyaml
• Changelog: https://pyup.io/changelogs/pyyaml/
• Homepage: http://pyyaml.org/wiki/PyYAML