There is no python-sphinx >= 1.7 for Leap 15.0.
After many requests to provide a package for Leap, I decided to ship a version
without docs.
diff -urEbwB kitty-0.12.3/setup.py kitty-0.12.3.new/setup.py
--- kitty-0.12.3/setup.py	2018-09-29 05:45:40.000000000 +0200
+++ kitty-0.12.3.new/setup.py	2018-11-27 09:55:13.030071308 +0100
@@ -625,8 +625,6 @@
     safe_makedirs(launcher_dir)
     build_linux_launcher(args, launcher_dir, for_bundle, sh_launcher, args.for_freeze)
     if not is_macos:  # {{{ linux desktop gunk
-        copy_man_pages(ddir)
-        copy_html_docs(ddir)
         icdir = os.path.join(ddir, 'share', 'icons', 'hicolor', '256x256', 'apps')
         safe_makedirs(icdir)
         shutil.copy2('logo/kitty.png', icdir)
@@ -813,8 +811,6 @@
         )
     elif args.action == 'linux-package':
         build(args, native_optimizations=False)
-        if not os.path.exists(os.path.join(base, 'docs/_build/html')):
-            run_tool(['make', 'docs'])
         package(args)
     elif args.action == 'osx-bundle':
         build(args, native_optimizations=False)