Resolve case sensitivity issues in io.read_xml_config

[oyvfoss]

io.read_xml_config <- io.hexfile crashes for file names with mixed case (a la Sta001.hex,Sta001.XMLCOM)

• In the above case, Sta001.hex is specified; function looks for STA001.XMLCON alternatively sta001.XMLCON.
• Mixed case prefix is common in datasets I have seen.

---> Should modify io.read_xml_config be case agnostic..

Example:

import ctdproc as ctd
hexfile = Path('./data/Sta0001.hex')
c = ctd.io.CTDHex(hexfile)

This works if I rename Sta0001.XMLCON to STA0001.XMLCON or sta0001.XMLCON. If not, I get the error below.

Resulting output

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
File ~/work/code/python/ctdproc/ctdproc/io.py:436, in CTDHex.read_xml_config(self)
    435 try:
--> 436     with open(self.xmlfile) as fd:
    437         tmp = xmltodict.parse(fd.read())

FileNotFoundError: [Errno 2] No such file or directory: 'data/sta0001.XMLCON'

During handling of the above exception, another exception occurred:

FileNotFoundError                         Traceback (most recent call last)
Cell In[10], line 3
      1 import ctdproc as ctd
      2 hexfile = Path('./data/Sta0001.hex')
----> 3 c = ctd.io.CTDHex(hexfile)

File ~/work/code/python/ctdproc/ctdproc/io.py:82, in CTDHex.__init__(self, filename)
     73 self._mapunits_freq = dict(
     74     t1="°C",
     75     t2="°C",
   (...)
     78     p="dbar",
     79 )
     81 # extract all data and metadata and convert to physical units
---> 82 self._extract_physical_data()

File ~/work/code/python/ctdproc/ctdproc/io.py:85, in CTDHex._extract_physical_data(self)
     84 def _extract_physical_data(self):
---> 85     self.read_xml_config()
     86     self.parse_hex()
     87     self.physicalunits()

File ~/work/code/python/ctdproc/ctdproc/io.py:439, in CTDHex.read_xml_config(self)
    437         tmp = xmltodict.parse(fd.read())
    438 except OSError as e:
--> 439     raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), e.filename)
    440 sa = tmp["SBE_InstrumentConfiguration"]["Instrument"]["SensorArray"]["Sensor"]
    441 # parse only valid sensors

FileNotFoundError: [Errno 2] No such file or directory: 'data/sta0001.XMLCON'

<\details>

[oyvfoss]

.. I now see that this has been an issue before (#13 ), but it still throws an error on my (Linux) system. Could be resolved by adding another if/elif clause or something, but I am sure there are neater ways of doing it.