'Create a subdirectory of the base temporary directory and return it.
If ``numbered``, ensure the directory is unique by adding a number
prefix greater than any existing one.'

def mktemp(self, basename, numbered=True):

    basetemp = self.getbasetemp()
    if (not numbered):
        p = basetemp.mkdir(basename)
    else:
        p = py.path.local.make_numbered_dir(prefix=basename, keep=0, rootdir=basetemp, lock_timeout=None)
    self.trace('mktemp', p)
    return p
