[2.7] bpo-33670: Expose Sphinx errorlevel (GH-7156). (GH-7201)

(cherry picked from commit 8c1ad0c4)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

Doc/make.bat

@@ -13,7 +13,7 @@ if not defined SPHINXBUILD if defined PYTHON (
         %PYTHON% -m pip install sphinx
         if errorlevel 1 exit /B
     )
-    set SPHINXBUILD=%PYTHON% -c "import sphinx, sys; sys.argv[0] = 'sphinx-build'; sphinx.main()"
+    set SPHINXBUILD=%PYTHON% -c "import sphinx, sys; sys.argv[0] = 'sphinx-build'; sys.exit(sphinx.main())"
 )
 
 if not defined PYTHON set PYTHON=py