Distance fails to start measuring

[greenfeld]

Distance-29 fails to start measuring on OLPC 11.3.0 os2.

Both the starting computer and the one joining the shared session log the following exception:

Traceback (most recent call last):

File "/home/olpc/Activities/Distance.activity/activity.py", line 291, in _helper_thread

dt = arange.measure_dt_seq(self.main_socket, self.initiating, self._change_message)

File "/home/olpc/Activities/Distance.activity/arange.py", line 418, in measure_dt_seq

mls = compute_mls(R)

File "/home/olpc/Activities/Distance.activity/arange.py", line 84, in compute_mls

return LFSR(Rf, [i - 1 for i in taps[n]], 2n - 1)

NameError: global name 'Rf' is not defined

[walter]

patch to remove spurious 'f' characters scattered throughout the file