Merge pull request #1 from kdudka/kdudka

kdudka
pycurl.c: eliminate duplicated code in util_write_callback()

Suggested by Zdenek Pavlas <https://bugzilla.redhat.com/857875#c8>.
pycurl.c: allow to use CURL_WRITEFUNC_PAUSE

... and returning -1 from the write call-back to abort the transfer

Reported By: Zdenek Pavlas
Bug: https://bugzilla.redhat.com/857875