All demos should either run or exit gracefully when run in parallel. Current status:
[OK] = runs perfectly
[ok] = exits gracefully
[??] = untested
[**] = fails
[OK] demo/fem/assembly/cpp
[ok] demo/fem/simple/cpp
[ok] demo/fem/simple/python
[ok] demo/function/eval/cpp
[ok] demo/function/eval/python
[ok] demo/function/nonmatching-interpolation/cpp
[OK] demo/function/nonmatching-interpolation/python
[OK] demo/function/projection-interpolation/python
[OK] demo/function/restriction/python
[OK] demo/la/block-matrix/cpp
[OK] demo/la/block-matrix/python
[OK] demo/la/eigensolver/cpp
[OK] demo/la/eigensolver/python
[OK] demo/la/trilinos/python
[ok] demo/mesh/ale/cpp
[OK] demo/mesh/ale/python
[OK] demo/mesh/built-in/python
[OK] demo/mesh/intersection/cpp
[OK] demo/mesh/intersection/python
[ok] demo/mesh/meshfunction/cpp
[OK] demo/mesh/meshfunction/python
[OK] demo/mesh/partitioning/cpp
[OK] demo/mesh/partitioning/python
[ok] demo/mesh/refinement/cpp
[ok] demo/mesh/refinement/python
[OK] demo/mesh/subdomains/cpp
[OK] demo/mesh/subdomains/python
[ok] demo/mesh/submesh/cpp
[OK] demo/mesh/submesh/python
[ok] demo/ode/aliev-panfilov/cpp
[ok] demo/ode/collection/cpp
[ok] demo/ode/complex/cpp
[ok] demo/ode/courtemanche/cpp
[ok] demo/ode/harmonic/cpp
[ok] demo/ode/lorenz/cpp
[ok] demo/ode/reaction/cpp
[ok] demo/ode/tentusscher/cpp
[OK] demo/parameters/cpp
[OK] demo/parameters/python
[ok] demo/pde/adaptive-poisson/python
[ok] demo/pde/advection-diffusion/cpp
[ok] demo/pde/advection-diffusion/python
[ok] demo/pde/bcs/cpp
[ok] demo/pde/bcs/python
[ok] demo/pde/curl-curl/cpp
[OK] demo/pde/curl-curl/python
[ok] demo/pde/dg/advection-diffusion/cpp
[OK] demo/pde/dg/advection-diffusion/python
[ok] demo/pde/dg/biharmonic/cpp
[ok] demo/pde/dg/biharmonic/python
[ok] demo/pde/dg/poisson/cpp
[OK] demo/pde/dg/poisson/python
[ok] demo/pde/dielectric/python
[ok] demo/pde/elasticity/cpp
[OK] demo/pde/elasticity/python
[OK] demo/pde/elastodynamics/cpp
[ok] demo/pde/equality/cpp
[OK] demo/pde/functional/cpp
[OK] demo/pde/functional/python
[OK] demo/pde/lift-drag/cpp
[OK] demo/pde/lift-drag/python
[ok] demo/pde/mixed-poisson/cpp
[OK] demo/pde/mixed-poisson/python
[ok] demo/pde/nonlinear-poisson/cpp
[OK] demo/pde/nonlinear-poisson/python
[OK] demo/pde/optimization/python
[ok] demo/pde/periodic/cpp
[ok] demo/pde/periodic/python
[ok] demo/pde/poisson1D/cpp
[OK] demo/pde/poisson1D/python
[ok] demo/pde/poisson/cpp
[OK] demo/pde/poisson/python
[ok] demo/pde/simple/cpp
[OK] demo/pde/simple/python
[ok] demo/pde/st[ok]es/stabilized/cpp
[ok] demo/pde/st[ok]es/stabilized/python
[ok] demo/pde/st[ok]es/taylor-hood/cpp
[ok] demo/pde/st[ok]es/taylor-hood/python
[ok] demo/pde/sym-dirichlet-bc/cpp
[OK] demo/pde/sym-dirichlet-bc/python
[OK] demo/pde/waveguide/cpp
[OK] demo/pde/waveguide/python
[ok] demo/plot/cpp
[OK] demo/plot/python
Seems to work now so I'm closing this bug.