bug#30093: Installing python-ipython breaks Gnome on Fedora.

[Fis Trivial]

* Environment
I am currently running Guix on top of Fedora 26, which comes with Gnome 3.24.2

As recommended(1), I source *~/.guix-profile/etc/profile* in *~/.bash_profile*
to make all the exported variables recognized by login shell.

* Issue
After installing python-ipython with guix, guix exported the following
variables:

        GUIX_GTK3_PATH
        PKG_CONFIG_PATH

The next time I login, Gnome was broken, displaying nothing but a black screen,
except for Owncloud client(which is based on Qt). And all the key bindings
are gone.

So, I used tty to move the `source` command from *.bash_profile* to *.bashrc*.
After that, Gnome came back and functions as usual.


* Version
$: guix --version
guix (GNU Guix) d9a38cc255d853b2694a01b5704c1daedbb56742


[1]: https://lists.gnu.org/archive/html/help-guix/2017-05/msg00072.html