Log Message:
py-yarl: updated to 1.4.2

1.4.1:
* Fix regression, make the library work on Python 3.5 and 3.6 again.

1.4.0:
* Distinguish an empty password in URL from a password not provided at all
* Fixed annotations for optional parameters of ``URL.build``
* Use None as default value of ``user`` parameter of ``URL.build``
* Enforce building C Accelerated modules when installing from source tarball, use
  ``YARL_NO_EXTENSIONS`` environment variable for falling back to (slower) Pure \ 
Python
  implementation
* Drop Python 3.5 support
* Fix quoting of plus in path by pure python version
* Don't create a new URL if fragment is unchanged
* Included in error msg the path that produces starting slash forbidden error
* Skip slow IDNA encoding for ASCII-only strings