dot2tex exits with status 0 (success) on error

[CyberShadow]

$ touch a
$ dot2tex a
ERROR    Parse error:

^
Expected {'graph' | 'digraph'}  (at char 0), (line:1, col:1)
ERROR    Failed to parse the input data. Is it a valid dot file?
Try to input xdot data directly. Example:
    dot -Txdot file.dot | dot2tex > file.tex

If this does not work, check that you have an updated version of PyParsing and
Graphviz. Users have reported problems with old versions. You can also run
dot2tex in debug mode using the --debug option:
    dot2tex --debug file.dot
A file dot2tex.log will be written to the current directory with detailed
information useful for debugging.
$ echo $?
0

This causes problems when running the software in a Makefile - bad/incomplete output is considered valid by build systems, and ends up cached and fed as input to other tools, which then result in confusing errors.