Test Emacs environment on startup.

Patch by Diego N. Barbato

--- a/telega.el	2020-02-07 17:07:18.549970090 +0100
+++ b/telega.el	2020-02-07 17:10:08.383499765 +0100
@@ -82,6 +82,7 @@
   "Start telegramming.
 If prefix ARG is given, then will not pop to telega root buffer."
   (interactive "P")
+  (telega-test-env t)
   (telega--create-hier)
 
   (unless (telega-server-live-p)
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<div class='path'>path: <a href='/guix/log/?id=10717c59aebfc8e0b77795b54eaea3160ea0cb03'>root</a>/<a href='/guix/log/gnu?id=10717c59aebfc8e0b77795b54eaea3160ea0cb03'>gnu</a>/<a href='/guix/log/gnu/installer?id=10717c59aebfc8e0b77795b54eaea3160ea0cb03'>installer</a>/<a href='/guix/log/gnu/installer/proxy.scm?id=10717c59aebfc8e0b77795b54eaea3160ea0cb03'>proxy.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/installer/proxy.scm?id=10717c59aebfc8e0b77795b54eaea3160ea0cb03&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-12-11 21:37:07 +0100'>2020-12-11</span></td><td><a href='/guix/commit/gnu/installer/proxy.scm?id=8361817bf693742757b096468198626f297bb09e'>install: Discover local substitute servers.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/substitutes.scm: New file.
* gnu/installer/newt/substitutes.scm: New file.
* gnu/local.mk (INSTALLER_MODULES): Add them.
* po/guix/POTFILES.in: Add gnu/installer/newt/substitutes.scm.
* gnu/installer/proxy.scm (with-silent-shepherd): Move to ...
* gnu/installer/utils.scm: ... here.
* gnu/installer/record.scm (&lt;installer&gt;)[substitutes-page]: New field.
* gnu/installer/newt.scm (substitutes-page): New procedure,
(newt-installer): register it.
* gnu/installer.scm (installer-steps): Add "substitutes-page" step.
* gnu/system/install.scm (%installation-services): Add avahi-service-type and
enable substitute server discover in guix-service-type.
[&lt;name-service-switch&gt;]: Set it to %mdns-host-lookup-nss.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-04-08 10:24:02 +0200'>2020-04-08</span></td><td><a href='/guix/commit/gnu/installer/proxy.scm?id=ee0ad7803c82383ac1bced073d8670bc407797e7'>installer: Add proxy support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/proxy.scm: New file.
* gnu/local.mk (INSTALLER_MODULES): Add it.
* po/guix/POTFILES.in: Add it.
* gnu/installer/newt/parameters.scm (run-proxy-page): New procedure,
(run-parameters-page): add the previous procedure to the parameters menu.
</span></span></td><td>Mathieu Othacehe</td></tr>