Format the given block of text, trimming leading/trailing
    empty lines and any leading whitespace that is common to all lines.
    The purpose is to let us list a code block as a multiline,
    triple-quoted Python string, taking care of indentation concerns.

def format_block(block):
    '''
    Format the given block of text, trimming leading/trailing
    empty lines and any leading whitespace that is common to all lines.
    The purpose is to let us list a code block as a multiline,
    triple-quoted Python string, taking care of indentation concerns.
    '''
    # separate block into lines
    lines = str(block).split('\n')
    # remove leading/trailing empty lines
    while lines and not lines[0]:
        del lines[0]
    while lines and not lines[-1]:
        del lines[-1]
    # look at first line to see how much indentation to trim
    ws = re.match(r'\s*', lines[0]).group(0)
    if ws:
        lines = map(lambda x: x.replace(ws, '', 1), lines)
    # remove leading/trailing blank lines (after leading ws removal)
    # we do this again in case there were pure-whitespace lines
    while lines and not lines[0]:
        del lines[0]
    while lines and not lines[-1]:
        del lines[-1]
    return '\n'.join(lines) + '\n'