Search cannot be canceled

[bllngr]

When a search is taking too long, it should be able to cancel it using Ctrl+C. This doesn't work (at least in Windows cmd/Powershell):

git_vanity.py DEC1A551F1ED
Attempting to find sha1 prefix `DEC1A551F1ED'
for commit `302e61425849fbfa779a9bb34a44673fe42cafbf'
[...]
Processing GS iteration 1
   Time:         0:00:00
   Last Speed:   N/A MH/s      (Avg: N/A MH/s)
   Tries remaining (optimistic):  100.000000% ...
   Chance (CDF):                  0.000000% ...
Processing GS iteration 11
   Time:         0:00:01.039226
   Last Speed:   40.4375 MH/s     (Avg: 40.3599 MH/s)
   Tries remaining (optimistic):  99.999985% ...
   Chance (CDF):                  0.000015% ...
From cffi callback <function _py_ref at 0x000001E8E92D6840>:
Traceback (most recent call last):
  File "C:\Python37\lib\site-packages\pyopencl\cffi_cl.py", line 72, in _py_ref
    @_ffi.callback('void*(void*)')
KeyboardInterrupt
Processing GS iteration 21
   Time:         0:00:02.065515
   Last Speed:   40.9083 MH/s     (Avg: 40.6127 MH/s)
   Tries remaining (optimistic):  99.999970% ...
   Chance (CDF):                  0.000030% ...

...and it just continues running. The only way to stop it is to kill the terminal or the python process.