'Download, unpack and install a single package.
If output is given it should be a file-like object and it
will receive a log of what happened.'

def installSinglePackage(self, output=None):

    if (not self._dict.get('Download-URL')):
        return ('%s:    This    package    needs    to    be    installed    manually    (no    Download-URL    field)' % self.fullname())
    msg = self.downloadPackageOnly(output)
    if msg:
        return ('%s:    download:    %s' % (self.fullname(), msg))
    msg = self.unpackPackageOnly(output)
    if msg:
        return ('%s:    unpack:    %s' % (self.fullname(), msg))
    return self.installPackageOnly(output)
