Improve error when executing `run.sh` from wrong directory

[BenjaminRodenberg]

I think for every (?) run.sh file it is necessary to run it from the folder of the participant (e.g. partitioned-heat-conduction/dirichlet-fenics). Running ./dirichlet-fenics/run.sh from partitioned-heat-conduction is incorrect and results in the error:

ERROR: Could not open requirements file: [Errno 2] No such file or directory: '../solver-fenics/requirements.txt'

Is it possible to improve this error? Basically we have to make sure that we always execute run.sh from its parent directory.