symbol '_' not allowed

д_ругойтест.рф
Codepoint U+005F at position 2 of 'д_ругойтест' not allowed

Full traceback:

Traceback (most recent call last):
  File "/home/user/somedirectory/code.py", line 34, in <module>
    punnycode_to_replace = idna.encode("д_ругойтест.рф")
  File "/usr/local/lib/python3.5/dist-packages/idna/core.py", line 355, in encode
    result.append(alabel(label))
  File "/usr/local/lib/python3.5/dist-packages/idna/core.py", line 276, in alabel
    check_label(label)
  File "/usr/local/lib/python3.5/dist-packages/idna/core.py", line 253, in check_label
    raise InvalidCodepoint('Codepoint {0} at position {1} of {2} not allowed'.format(_unot(cp_value), pos+1, repr(label)))
idna.core.InvalidCodepoint: Codepoint U+005F at position 2 of 'д_ругойтест' not allowed
[Finished in 0.4s with exit code 1]

[jrlevine]

the _labels are not host names. Also, since they start with an underscore rather than xn-- IDNA obviously doesn’t apply to them.

[sebschrader]

It should be noted that SRV record labels do contain underscores (e.g. _ldap._tcp.example.com).