Use xlsx file object instead of absolute path

[KipSigei]

Signed-off-by: Kipchirchir Sigei [email protected]

Changes / Features implemented

• Upadate to use file object intsead of absolute file path when loading excel workbook

Steps taken to verify this change does what is intended

• The following exception is being thrown when uploading a form with external choices

File "/srv/onadata/./onadata/apps/viewer/models/data_dictionary.py", line 246, in set_object_permissions
    f = sheet_to_csv(instance.xls, "external_choices")
  File "/srv/onadata/./onadata/apps/viewer/models/data_dictionary.py", line 76, in sheet_to_csv
    workbook = openpyxl.load_workbook(xls_content.path)
  File "/usr/local/lib/python3.9/dist-packages/django/db/models/fields/files.py", line 59, in path
    return self.storage.path(self.name)
  File "/usr/local/lib/python3.9/dist-packages/django/core/files/storage.py", line 128, in path
    raise NotImplementedError("This backend doesn't support absolute paths.")

Side effects of implementing this change

Before submitting this PR for review, please make sure you have:

• Included tests
• Updated documentation

Closes #2258

[ukanga]

Why is the change necessary? Do we have a test that should have captured this issue? Maybe we are missing a test.

[KipSigei]

@ukanga i was unable to test this locally, there already exists a test case for external choices form and it seems to be passing