Building PETSc with Python 3 fails

[johannesring]

When building PETSc with Python 3, I get the following error:

[petsc] Configure does not support Python 3 yet, please run as
[petsc]   python2 './configure' '--prefix=/home/johannr/.hashdist/bld/petsc/dq4zt55md7w7' 'COPTFLAGS=-O2' '--with-shared-libraries=1' '--with-debugging=0' '--with-ssl=0' '--with-blas-lapack-lib=/home/johannr/.hashdist/bld/blas/ga3yotglkobk/lib/libopenblas.so' '--with-metis-dir=/home/johannr/.hashdist/bld/parmetis/d5rx62dqsmbh' '--with-parmetis-dir=/home/johannr/.hashdist/bld/parmetis/d5rx62dqsmbh' '--with-scotch-dir=/home/johannr/.hashdist/bld/scotch/vm3qczcxeszc' '--with-ptscotch-dir=/home/johannr/.hashdist/bld/scotch/vm3qczcxeszc' '--with-suitesparse=1' '--with-suitesparse-include=/home/johannr/.hashdist/bld/suitesparse/psbs2mcuk4dc/include/suitesparse' '--with-suitesparse-lib=[/home/johannr/.hashdist/bld/suitesparse/psbs2mcuk4dc/lib/libumfpack.a,libklu.a,libcholmod.a,libbtf.a,libccolamd.a,libcolamd.a,libcamd.a,libamd.a,libsuitesparseconfig.a]' '--with-hypre=1' '--with-hypre-include=/home/johannr/.hashdist/bld/hypre/3sialo4py6ds/include' '--with-hypre-lib=/home/johannr/.hashdist/bld/hypre/3sialo4py6ds/lib/libHYPRE.so' '--with-mpi-compilers' 'CC=/home/johannr/.hashdist/bld/mpi/gmkx3ftk3tz2/bin/mpicc' 'CXX=/home/johannr/.hashdist/bld/mpi/gmkx3ftk3tz2/bin/mpic++' 'F77=/home/johannr/.hashdist/bld/mpi/gmkx3ftk3tz2/bin/mpif77' 'F90=/home/johannr/.hashdist/bld/mpi/gmkx3ftk3tz2/bin/mpif90' 'FC=/home/johannr/.hashdist/bld/mpi/gmkx3ftk3tz2/bin/mpif90' '--with-patchelf-dir=/home/johannr/.hashdist/bld/patchelf/k3rloj265ogt' '--with-python-dir=/home/johannr/.hashdist/bld/python/vgno2o47k5xs' '--with-superlu_dist-dir=/home/johannr/.hashdist/bld/superlu_dist/zddesa3hyero' '--download-mumps=1' '--download-scalapack=1' '--download-blacs=1' '--download-ml=1'
[petsc|ERROR] Command '[u'/bin/bash', '_hashdist/build.sh']' returned non-zero exit status 1
[petsc|ERROR] command failed (code=1); raising

The fix is simple: run the configure script with Python 2 (python2 ./configure ...). But how to do that in HashStack?