Return first found file matching name (case-insensitive).

        Some packages have docs/HISTORY.txt and
        package/name/HISTORY.txt.  We make sure we only return the one
        in the docs directory if no other can be found.

        'names' can be a string or a list of strings; if you have both
        a CHANGES.txt and a docs/HISTORY.txt, you want the top level
        CHANGES.txt to be found first.

def filefind(self, names):
        """Return first found file matching name (case-insensitive).

        Some packages have docs/HISTORY.txt and
        package/name/HISTORY.txt.  We make sure we only return the one
        in the docs directory if no other can be found.

        'names' can be a string or a list of strings; if you have both
        a CHANGES.txt and a docs/HISTORY.txt, you want the top level
        CHANGES.txt to be found first.
        """
        if type(names) is str:
            names = [names]
        lower_names = []
        for name in names:
            lower_names.append(name.lower())
        names = lower_names
        files = self.list_files()
        found = []
        for fullpath in files:
            filename = os.path.basename(fullpath)
            if filename.lower() in names:
                logger.debug("Found %s", fullpath)
                if not os.path.exists(fullpath):
                    # Strange.  It at least happens in the tests when
                    # we deliberately remove a CHANGES.txt file.
                    logger.warn("Found file %s in version control but not on "
                                "file system.", fullpath)
                    continue
                found.append(fullpath)
        if not found:
            return
        if len(found) > 1:
            found.sort(key=len)
            logger.warn("Found more than one file, picked the shortest one to "
                        "change: %s", ', '.join(found))
        return found[0]