Comment 2 for bug 1394453

it is not strange, because strip deals with characters, not string, see: https://docs.python.org/2/library/string.html#string.strip

here is an example:

>>> 'HTTP_AAAPH'.strip('HP')
'TTP_AAA'

it means, remove all characters of ('H', 'P') in the leading and trailing characters, so even `PH` is not match `HP`, **they** are removed too