"--at-once" option

Hi,

I can't seem to get the "--at-once" option working. My OS is "Linux Mint 17 Qiana".
I'm not really sure what version of Python is being used. "python2.7 -V" gives "Python 2.7.16", but When I do "python -V" gives "Python 2.7.6". I tested on a file containing "hello\nthere". It seems to find the match, but not do any changes:

repren -p toss_repren --at-once -i ./toss.txt
Using 1 patterns:
'hello' -> 'goodbye'
Found 1 files in: ./toss.txt
Read 1 files (12 chars), found 1 matches (0 skipped due to overlaps)
Changed 0 files (0 rewritten and 0 renamed)

When I drop the "--at-once" option, it works:

repren -p toss_repren -i ./toss.txt
Using 1 patterns:
'hello' -> 'goodbye'
Found 1 files in: ./toss.txt
- modify: ./toss.txt: 1 matches
Read 1 files (12 chars), found 1 matches (0 skipped due to overlaps)
Changed 1 files (1 rewritten and 0 renamed)

I also did "bash run.sh" to run the tests. Most seemed to work but at the end I got "ls_portable test2
tail: cannot open ‘+2’ for reading: No such file or directory". Thanks in advance for your help.