We are installing from scratch and get the following; access to brew is in order:

...

/usr/local/Cellar/libtool/2.4.6_1/share/man/ (2 files)

Creating firedrake virtualenv in 'firedrake'.

ERROR: The executable firedrake/bin/python2.7 is not functioning

ERROR: It thinks sys.prefix is u'/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7' (should be u'/Users/amtob/werk/firedrake')

ERROR: virtualenv is not compatible with this system or executable