ACT fails to run read_arm_mmcr when using read-only files as input

[isilber]

• ACT version: 2.1.4
• Python version: 3.11.5
• Operating System: Red Hat v7.9

Description

ACT fails to run read_arm_mmcr when using read-only files as input

What I Did

Upon running the following code:

import act
filename = './sgpmmcrmomC1.b1.20030927.000000.cdf'
mmcr_file = act.io.read_arm_mmcr([filename])
mmcr_file

I receive the following error:

OSError                                   Traceback (most recent call last)
Cell In[1], line 3
      1 import act
      2 filename = './sgpmmcrmomC1.b1.20030927.000000.cdf'
----> 3 mmcr_file = act.io.read_arm_mmcr([filename])
      5 mmcr_file

File ~/git_dev/ACT/act/io/arm.py:844, in read_arm_mmcr(filenames)
    842 multi_ds = []
    843 for f in filenames:
--> 844     nc = Dataset(f, 'a')
    845     # Change heights name to range to read appropriately to xarray
    846     if 'heights' in nc.dimensions:

File src/netCDF4/_netCDF4.pyx:2521, in netCDF4._netCDF4.Dataset.__init__()

File src/netCDF4/_netCDF4.pyx:2158, in netCDF4._netCDF4._ensure_nc_success()

OSError: [Errno 30] Read-only file system: './sgpmmcrmomC1.b1.20030927.000000.cdf'