Hi Guix,

attached is a patch to fix the install-doc phase of python-matplotlib.
Since UTF locales are no longer available by default the install-doc
phase fails as it depends on setting the locale to en_US.UTF-8.

The attached patch installs the locale before it is set, thereby fixing
the phase.

We likely won't be able to see the effect of this fix on hydra because
numpy fails to build, which is an input to matplotlib, but at least
matplotlib can now be compiled locally.

~~ Ricardo