one more try

.travis.yml

@@ -76,7 +76,7 @@ install:
 
   - if [[ "$TRAVIS_PYTHON_VERSION" == "3.8" ]]; then
       conda install nlopt mpi4py scipy mpich;
-      export PETSC_CONFIGURE_OPTIONS='--with-batch';
+      export PETSC_CONFIGURE_OPTIONS='--with-mpi=0 --with-batch';
       pip install petsc petsc4py;
     else
       conda install nlopt petsc4py petsc $MUMPS mpi4py scipy $MPI;