pexpect.spawn hangs when cwd is used but the directory doesn't exist

[jsolbrig]

I ran into an issue where I was calling pexpect.spawn with the cwd keyword, but had forgotten to create the directory referenced by that keyword. When called, the process just hangs, even if timeout is set.

For example, this appears to hang indefinitely:

import pexpect
proc = pexpect.spawn("ls -la", cwd="./does_not_exist", timeout=1)

This works as expected:

import os, pexpect
os.mkdirs("./exists")
proc = pexpect.spawn("ls -la", cwd="./exists", timeout=1)