OSError in Subprocess

[connordavenport]

This might be an edge case but I am attempting to build a family with a very large amount of fonts. My build script uses the execute function in the FDKBridge.py but breaks around 125 fonts with the following error: OSError: [Errno 24] Too many open files. It seems to be a problem with the line where popen is declared.

ufo2fdk/Lib/ufo2fdk/fdkBridge.py

Line 273 in 37a5a3a

popen = subprocess.Popen(cmds, stderr=stderrFile, stdout=stdoutFile, env=env, shell=True)

This could also just very well be a problem on my end. TIA