Copy a main repository to a new location.

def clone(cls, srcpath, destpath):
        """Copy a main repository to a new location."""
        try:
            os.makedirs(destpath)
        except OSError as e:
            if not e.errno == errno.EEXIST:
                raise
        cmd = [SVNADMIN, 'dump', '--quiet', '.']
        dump = subprocess.Popen(
               cmd, cwd=srcpath, stdout=subprocess.PIPE,
               stderr=subprocess.PIPE,
        )
        repo = cls.create(destpath)
        repo.load(dump.stdout)
        stderr = dump.stderr.read()
        dump.stdout.close()
        dump.stderr.close()
        dump.wait()
        if dump.returncode != 0:
            raise subprocess.CalledProcessError(dump.returncode, cmd, stderr)
        return repo