MCPL extension in incident beam path causes error in mcvine

If the incident beam file has a .mcpl extension, then mcvine is going down a different path than if it does not have the extension.

Example run from docker container images (never running Mantid either time before):

This is output if I use the file called test.mcpl, which shows an error:

(base) root@016e5134cda7:/opt/mcvine# mcu_sample_simulator NOMAD ./tests/test_data/test.mcpl ./tests/test_data/test_dir/
SCRIPT: /opt/conda/lib/python3.9/site-packages/mcu_sample_simulator/instruments/nomad/instrument.py
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mutiple_scattering'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'nodes'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mpiSize'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mpiRank'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
Traceback (most recent call last):
  File "/opt/conda/bin/mcvine", line 6, in <module>
    from mcvine.cli import mcvine
  File "/opt/conda/lib/python3.9/site-packages/mcvine/cli/__init__.py", line 75, in <module>
    from mcvine.instruments import cli
  File "/opt/conda/lib/python3.9/site-packages/mcvine/instruments/cli.py", line 19, in <module>
    importlib.import_module(mod)
  File "/opt/conda/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/opt/conda/lib/python3.9/site-packages/mcvine/instruments/SEQUOIA/__init__.py", line 4, in <module>
    from . import mantid2mcvine # make sure mantid IDF is there
  File "/opt/conda/lib/python3.9/site-packages/mcvine/instruments/SEQUOIA/mantid2mcvine.py", line 29, in <module>
    install_mantid_IDF()
  File "/opt/conda/lib/python3.9/site-packages/mcvine/instruments/SEQUOIA/mantid2mcvine.py", line 26, in install_mantid_IDF
    im.mantid_install()
  File "/opt/conda/lib/python3.9/site-packages/mantid2mcvine/__init__.py", line 128, in mantid_install
    instrument_xml.install_mantid_xml_to_userhome(self.mantid_idf, beamline=self.beamline, mantid_instr_dir=target)
  File "/opt/conda/lib/python3.9/site-packages/mantid2mcvine/instrument_xml/__init__.py", line 24, in install_mantid_xml_to_userhome
    raise RuntimeError(msg)
RuntimeError: Mantid has to be installed and run for at least one time for mantid2mcvine to work

Yet, if I rename that file to test_mcpl with no extension, then it will run:

(base) root@016e5134cda7:/opt/mcvine# mv ./tests/test_data/test.mcpl tests/test_data/test_mcpl
(base) root@016e5134cda7:/opt/mcvine# mcu_sample_simulator NOMAD ./tests/test_data/test_mcpl ./tests/test_data/test_dir/
SCRIPT: /opt/conda/lib/python3.9/site-packages/mcu_sample_simulator/instruments/nomad/instrument.py
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mutiple_scattering'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'nodes'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mpiSize'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:178: UserWarning: Unrecognized kwd: 'mpiRank'
  warnings.warn("Unrecognized kwd: {!r}".format(a))
weight:  1.0
/opt/conda/lib/python3.9/site-packages/mcvine/run_script.py:162: UserWarning: Developer: <mccomposite.mccompositebp.CompositeNeutronScatterer object at 0x74e6077f9b80> does not implement method "create_pps"
  warnings.warn('Developer: %s does not implement method "create_pps"' % comp)