fenics fails to install on current unstable as of Dec 18 2019

[rht]

Describe the bug
fenics fails to install with this error message:

builder for '/nix/store/6zyraw3jpd9aba418m419hf02bbcyp6d-python3.7-fiat-2017.1.0.drv' failed with exit code 127; last 10 log lines:
  /build/fiat-2017.1.0
  Finished executing pipInstallPhase
  post-installation fixup
  shrinking RPATHs of ELF executables and libraries in /nix/store/1i6adsv9cpwsis6zg9blkpdnk7fdymkz-python3.7-fiat-2017.1.0
  strip is /nix/store/a9ms1pkj00sgssxqr2cvryv3h5fki4an-binutils-2.31.1/bin/strip
  stripping (with command strip and flags -S) in /nix/store/1i6adsv9cpwsis6zg9blkpdnk7fdymkz-python3.7-fiat-2017.1.0/lib 
  patching script interpreter paths in /nix/store/1i6adsv9cpwsis6zg9blkpdnk7fdymkz-python3.7-fiat-2017.1.0
  checking for references to /build/ in /nix/store/1i6adsv9cpwsis6zg9blkpdnk7fdymkz-python3.7-fiat-2017.1.0...
  running install tests
  /nix/store/whpnlfj79vd8p175rp1bwg0x7wz5lmj1-stdenv-linux/setup: line 1299: py.test: command not found

To Reproduce
Run nix-build with allowUnsupportedSystem = true.

[rht]

Requesting @jamtrott to update fenics to 2019.1.0

[knedlsepp]

@rht @jamtrott Did try upgrading (and actually fixing stuff on Linux): master...knedlsepp:bump-fenics. Got most of it building (some things are known issues, e.g. incompatibility with newer pytest versions). I'm however still having trouble running a simple example, which crashes with a segmentation fault:

from fenics import *

mesh = UnitSquareMesh(8, 8)
V = FunctionSpace(mesh, 'P', 1)

u_D = Expression('1 + x[0]*x[0] + 2*x[1]*x[1]', degree=2)

def boundary(x, on_boundary):
    return on_boundary

bc = DirichletBC(V, u_D, boundary)

u = TrialFunction(V)
v = TestFunction(V)
f = Constant(-6.0)
a = dot(grad(u), grad(v))*dx
L = f*v*dx

u = Function(V)
solve(a == L, u, bc)

Any help welcome. (Currently thinking that there different versions of openBLAS in the closure, openblasCompat from numpy and openblas from suitesparse)