Port ninja fails to build due to pickle error in Python2

[EdHarry]

Port ninja fails at the build phase, in file configure.py at line 435:

proc = subprocess.Popen(['re2c', '-V'], stdout=subprocess.PIPE)

with

raise ValueError, "insecure string pickle"

using system python (2.7.10) on OSX 10.11

the offending line also produces the same error using macports python 2.7, however it behaves as expected using macports python 3.5. I can get the port to build using a custom portfile which uses macports python 3.5