TypeError while running scons tests for Galsim installation on macOS 10.12 with anaconda

Question

I am trying to install Galsim by following the instructions on https://github.com/GalSim-developers/GalSim/blob/master/INSTALL.md#0-overall-summary but keep getting the following typeerror when I reach the scons tests portion.

    Starting python tests...
    scons: *** [tests/tests.log] TypeError : write() argument must be str, not bytes
    Traceback (most recent call last):
    File "/Users/lorena/anaconda3/lib/scons-3.0.0/SCons/Action.py", line 1197, in execute
    result = self.execfunction(target=target, source=rsources, env=env)
    File "/Users/lorena/git/GalSim/tests/SConscript", line 81, in run_tests
    sys.stdout.write(buf)
    TypeError: write() argument must be str, not bytes
    scons: building terminated because of errors.

I'm using python 3.6.