piuparts_tap: explicitely set Encoding::UTF_8 for Ruby 1.9
piuparts_tap: explicitely set Encoding::UTF_8 for Ruby 1.9

On Debian/wheezy LANG and LC_ALL are empty by default (and therefore
defaulting to 'C' locale), running piuparts_tap therefore fails with:

| /usr/bin/piuparts_tap:26:in `gsub': invalid byte sequence in US-ASCII (ArgumentError)
| 	from /usr/bin/piuparts_tap:26:in `<main>'

The real fix would be to set LANG/LC_ALL accordingly, but we can't
control this from inside the piuparts_tap script, so let's
work around this issue by setting Encoding::UTF_8 explicitely.

Thanks: Christian Hofstaedtler <482bd64c6c9f098c9ef8b77b8f870517bf33a1b9@zeha.at> for feedback

tonin/jenkins-debian-glue,tonin/jenkins-debian-glue,jbfavre/jenkins-debian-glue,hashar/jenkins-debian-glue,zeha/jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,n054/jenkins-debian-glue,n054/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,webtrekk-kane/jenkins-debian-glue,bmiklautz/jenkins-debian-glue,hashar/jenkins-debian-glue,cclausen/jenkins-debian-glue,mika/jenkins-debian-glue,jbfavre/jenkins-debian-glue,mika/jenkins-debian-glue,webtrekk-kane/jenkins-debian-glue,vorlock/jenkins-debian-glue,hetznerZA/jenkins-debian-glue,zeha/jenkins-debian-glue,vorlock/jenkins-debian-glue,hetznerZA/jenkins-debian-glue,cclausen/jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,kartikm/jenkins-debian-glue,kartikm/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,bmiklautz/jenkins-debian-glue