Dont assume sphinx-build is a python script

Fixes #1561

docs/Makefile

@@ -3,7 +3,7 @@
 
 # You can set these variables from the command line.
 SPHINXOPTS    = -j auto -T $(FAIL_WARN)
-SPHINXBUILD   = python3 .. +launch :sphinx-build
+SPHINXBUILD   = sphinx-build
 SPHINXPROJ    = kitty
 SOURCEDIR     = .
 BUILDDIR      = _build

docs/conf.py

@@ -22,7 +22,11 @@ from sphinx import addnodes
 from sphinx.environment.adapters.toctree import TocTree
 from sphinx.util.logging import getLogger
 
-from kitty.constants import str_version
+kitty_src = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+if kitty_src not in sys.path:
+    sys.path.insert(0, kitty_src)
+if True:
+    from kitty.constants import str_version
 
 # config {{{
 # -- Project information -----------------------------------------------------