Update version number

    Returns a semantic_version object

def update_version_number(update_level='patch'):
    """Update version number

    Returns a semantic_version object"""

    """Find current version"""
    temp_file = version_file().parent / ("~" + version_file().name)
    with open(str(temp_file), 'w') as g:
        with open(str(version_file()), 'r') as f:
            for line in f:
                version_matches = bare_version_re.match(line)
                if version_matches:
                    bare_version_str = version_matches.groups(0)[0]
                    if semantic_version.validate(bare_version_str):
                        current_version = Version(bare_version_str)
                        print("{}Current version is {}".format(" "*4, current_version))
                    else:
                        current_version = Version.coerce(bare_version_str)
                        if not text.query_yes_quit("{}I think the version is {}. Use it?".format(" "*4, current_version), default="yes"):
                            exit(Fore.RED + 'Please set an initial version number to continue')

                    """Determine new version number"""
                    if update_level is 'major':
                        current_version = current_version.next_major()
                    elif update_level is 'minor':
                        current_version = current_version.next_minor()
                    elif update_level is 'patch':
                        current_version = current_version.next_patch()
                    elif update_level is 'prerelease':
                        if not current_version.prerelease:
                            current_version = current_version.next_patch()
                            current_version.prerelease = ('dev', )
                    else:
                        exit(Fore.RED + 'Cannot update version in {} mode'.format(update_level))

                    print("{}New version is     {}".format(" "*4, current_version))

                    """Update version number"""
                    line = '__version__ = "{}"'.format(current_version)
                print(line, file=g, end="")
        print('', file=g)  # add a blank line at the end of the file
    shutil.copyfile(str(temp_file), str(version_file()))
    os.remove(str(temp_file))
    return(current_version)