* gnu/packages/python-xyz.scm (python2-mechanize): Rename to ...
(python-mechanize): ... this. Update to 0.4.5.
[arguments]: Remove.
[propagated-inputs]: Add PYTHON-HTML5LIB.
[home-page]: Update to current.
[license]: Set to LICENSE:BSD-3.
(python2-mechanize): Define in terms of PACKAGE-WITH-PYTHON2.