def find_sphinx_build_dir():
build = glob.glob('<STR_LIT>', recursive=True)<EOL>if not build:<EOL><INDENT>raise RuntimeError("<STR_LIT>")<EOL><DEDENT>build_folder = build[<NUM_LIT:0>]<EOL>return build_folder<EOL>
Find build subfolder within sphinx docs directory.

This is called by :func:`commit_docs` if keyword arg ``built_docs`` is not
specified on the command line.