Build-depend on python3-sphinxcontrib.qthelp for sphinx >= 2.0

Closes: #955120

debian/changelog

@@ -1,3 +1,10 @@
+cmake (3.16.3-2) UNRELEASED; urgency=medium
+
+  * Build-depend on python3-sphinxcontrib.qthelp for sphinx >= 2.0
+    (Closes: #955120)
+
+ -- Felix Geyer <fgeyer@debian.org>  Tue, 14 Apr 2020 19:11:32 +0200
+
 cmake (3.16.3-1) unstable; urgency=medium
 
   * New upstream release. (Closes: #949964)

debian/control

@@ -16,7 +16,7 @@ Build-Depends: debhelper-compat (= 12),
                librhash-dev,
                libuv1-dev (>= 1.10),
                procps [!hurd-any],
-               python3-sphinx,
+               python3-sphinx (<< 2.0) | python3-sphinxcontrib.qthelp,
                qtbase5-dev <!stage1>,
                zlib1g-dev
 Rules-Requires-Root: no