DataCoverageError when running pyaeroval ana.run with var_list and multiple obs-setups

[heikoklein]

Describe the bug

• Pyaerocom version: 0.19++

• Configuration file (if applicable):
  cfg_emep-ex.py.gz

• Error message (if applicable):

Traceback (most recent call last):
  File "/home/heikok/Programme/Python/pyaerocom/pyaerocom/colocation/colocator.py", line 369, in run
    vars_to_process = self.prepare_run(var_list)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/heikok/Programme/Python/pyaerocom/pyaerocom/colocation/colocator.py", line 340, in prepare_run
    vars_to_process = self._filter_var_matches_varlist(vars_to_process, var_list)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/heikok/Programme/Python/pyaerocom/pyaerocom/colocation/colocator.py", line 473, in _filter_var_matches_varlist
    _subset = self._filter_var_matches_var_name(vars_to_process, var_name)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/heikok/Programme/Python/pyaerocom/pyaerocom/colocation/colocator.py", line 693, in _filter_var_matches_var_name
    raise DataCoverageError(var_name)
pyaerocom.exceptions.DataCoverageError: concNno2

It works in this example if one selects exactly the obs-network by name, e.g. obs_name="EBAS-d-tc", but in setups with more than 2 obs-networks where one wants to select a var_list of two variables from different obs-networks, this approach no longer works. It gets even more complicated, if variables only exist for certain time-steps in different obs-networks or require data from other obs-ids to calculate.

To Reproduce
Steps to reproduce the behavior:

1. create a configuration with different obs-vars in different obs-setups, here, "EBAS-d-tc" and "EBAS-d-ox"
2. ensure that ana.run() is working
3. rerun experiment with only one obs-variable ana.run(var_list=["concNno2"])

Expected behavior
The user can select variables in var_list without specifying the obs-name. The experiment is only run for these variable, and don't give an exeption if this variable is not available in all obs-networks (a warning is ok).

Additional context
Reported by sevaral users, e.g. @michaelgau
Independent of raise_exeptions=True/False