mini-dinstall: \"File contains parsing errors\"

While setting up mini-dinstall today, I tripped over this error:

$ mini-dinstall -b
Traceback (most recent call last):
  File "/usr/bin/mini-dinstall", line 205, in <module>
configp.read(configfile_names)
  File "/usr/lib/python2.7/ConfigParser.py", line 305, in read
self._read(fp, filename)
  File "/usr/lib/python2.7/ConfigParser.py", line 546, in _read
raise e
ConfigParser.ParsingError: File contains parsing errors: /home/hugh/.mini-dinstall.conf
    [line  2]: '    mail_to = sysadmin@example.com\n'
    [line  3]: '    incoming_permissions = 0755\n'
    [line  4]: '    architectures = all, amd64\n'
    [line  5]: '    archive_style = simple-subdir\n'
    [line  6]: '    dynamic_reindex = 1\n'
    [line  7]: '    archivedir = /home/hugh/public_html/debian/\n'

Eventually, I figured out the reason: leading spaces in each line. I'd assumed I could write the config file like so:

[section]
    # Notice the indentation!
    key = value
    otherkey = othervalue

but that's incorrect; it needs to be like so:

[section]
# Indentation is for suckers and chumps.  Apparently.
key = value
otherkey = othervalue

Hopefully that saves someone half an hour...