add file.close() to write_exact_solution_to_xdmf file

LDDsimulation/LDDsimulation.py

LDDsimulation/boundary_and_interface.py

RR-2-patch-test-case/RR-2-patch-test.py

...solution/RR-multi-patch-with-gravity-constant-solution.py

RR-multi-patch-plus-gravity/RR-multi-patch-with-gravity.py

...tion/RR-multi-patch-with-inner-patch-constant-solution.py

...-case-const-solution/TP-TP-layered_soil-const-solution.py

...ion/TP-TP-layered_soil_with_inner_patch_const_solution.py