See suggestion in https://github.com/bskinn/sphobjinv/issues/275

This prevents the module from creating an ssl context upon import, when,
during a build especially, a certificate file may not be present.  Otherwise
module import would fail.

--- a/src/sphobjinv/inventory.py
+++ b/src/sphobjinv/inventory.py
@@ -30,7 +30,6 @@ Sphinx |objects.inv| files.
 """
 
 import re
-import ssl
 import urllib.request as urlrq
 from zlib import error as zlib_error
 
@@ -218,8 +217,15 @@ class Inventory:
     #: zlib compression line for v2 |objects.inv| header
     header_zlib = "# The remainder of this file is compressed using zlib."
 
-    # Private class member for SSL context, since context creation is slow(?)
-    _sslcontext = ssl.create_default_context(cafile=certifi.where())
+    # Private class member for SSL context
+    _sslcontext_ = None
+
+    @property
+    def _sslcontext(self):
+        import ssl
+        if not self._sslcontext_:
+            self._sslcontext_ = ssl.create_default_context(cafile=certifi.where())
+        return self._sslcontext_
 
     @property
     def count(self):
4290766'>refs</a><a class='active' href='/guix/log/gnu/machine.scm'>log</a><a href='/guix/tree/gnu/machine.scm?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>tree</a><a href='/guix/commit/gnu/machine.scm?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>commit</a><a href='/guix/diff/gnu/machine.scm?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/machine.scm'>
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<div class='path'>path: <a href='/guix/log/?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>root</a>/<a href='/guix/log/gnu?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>gnu</a>/<a href='/guix/log/gnu/machine.scm?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766'>machine.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/machine.scm?id=c704bdd95bf72c2f74ca5daff18dfc1a84290766&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-25 19:11:36 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu/machine.scm?id=a5e2fc73760a2ae023f2e56bdbf8025971f90e64'>utils: Move &lt;location&gt; and '&amp;error-location' to (guix diagnostics).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/utils.scm (&lt;location&gt;, source-properties-&gt;location)
(location-&gt;source-properties, &amp;error-location): Move to...
* guix/diagnostics.scm: ... here.
* gnu.scm: Adjust imports accordingly.
* gnu/machine.scm: Likewise.
* gnu/system.scm: Likewise.
* gnu/tests.scm: Likewise.
* guix/inferior.scm: Likewise.
* tests/channels.scm: Likewise.
* tests/packages.scm: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-02-09 23:16:45 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/machine.scm?id=e81344428726f3dae5d2a2e7bb296f46fcde6cc5'>Update e-mail address for Jakob L. Kreuze.</a><span class='msg-avail'>...<span class='msg-tooltip'>As requested here:
&lt;https://lists.gnu.org/archive/html/guix-devel/2020-02/msg00128.html&gt;.

* .mailmap: Add an entry for Jakob.
* gnu/machine.scm, gnu/machine/digital-ocean.scm, gnu/machine/ssh.scm,
gnu/packages/admin.scm, gnu/packages/i2p.scm, gnu/packages/music.scm,
gnu/packages/web.scm, gnu/tests/reconfigure.scm, guix/scripts/deploy.scm,
guix/scripts/system/reconfigure.scm: Update their e-mail address.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-12-08 00:47:26 +0100'>2019-12-08</span></td><td><a href='/guix/commit/gnu/machine.scm?id=a1d7920861a8d6c6774149eaf939eb2636942090'>machine: Remove unnecessary record self-referencing bindings.</a><span class='msg-avail'>...<span class='msg-tooltip'>'this-machine' and 'this-machine-ssh-configuration' were useless given
that there are no thunked fields.

* gnu/machine.scm (&lt;machine&gt;)[this-machine]: Remove.
* gnu/machine/ssh.scm (&lt;machine-ssh-configuration&gt;)
[this-machine-ssh-configuration]: Remove.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-07 00:59:56 +0100'>2019-12-07</span></td><td><a href='/guix/commit/gnu/machine.scm?id=eaabc5e87f4e48d7bce88ca231f5fc2d554ca3d6'>machine: Add provenance tracking to each machine operating system.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm (&lt;machine&gt;): Rename accessor to
'%machine-operating-system'.
(machine-operating-system): New procedure.
* doc/guix.texi (Service Reference): Mention it.
</span></span></td><td>Ludovic Courtès</td></tr>