TextToDiff fails because pipes are closed on exec in Python >= 3.4

[edsnowden]

editrcs/src/editrcs/__init__.py

Line 231 in 14b1a12

if os.fork() == 0:

https://docs.python.org/3/library/os.html#inheritance-of-file-descriptors

Here's the fix

# since Python 3.4 newly-created file descriptors are closed on exec;
# make sure the ones we need survive
for fd in (src_r, dst_r, res_w):
    os.set_inheritable(fd, True)