get_cazyme_annotations.py CLI required arguments appear optional

[widdowquinn]

On branch CAZy_annotation_summary_frst_draft I get this error:

$ python3 pyrewton/genbank/get_cazyme_annotations/get_cazyme_annotations.py
Traceback (most recent call last):
  File "pyrewton/genbank/get_cazyme_annotations/get_cazyme_annotations.py", line 624, in <module>
    main()
  File "pyrewton/genbank/get_cazyme_annotations/get_cazyme_annotations.py", line 84, in main
    input_dir_get_cazyme_annotations.check_input(args, logger)
  File "/Users/lpritc/Library/Mobile Documents/com~apple~CloudDocs/Strathclyde_Work/Projects/PhD_EASTBIO_StAndrews/PhD_Project_Scripts/pyrewton/directory_handling/input_dir_get_cazyme_annotations.py", line 40, in check_input
    if (args.df_input).is_file() is False:
AttributeError: '_io.TextIOWrapper' object has no attribute ‘is_file'

This looks like df_input is a required argument for the script (hence the test for is_file(), but is being treated as an optional argument in the parser. An appropriate fix would be to make df_input a required argument.