tests: fix test-demandimport.py on Python 3.9
Starting with Python 3.9, importing importlib.resources (indirectly) imports
the zipfile module. Therefore, the module is not suitable for the test.
Instead, we can use the ftplib module, which is very unlikely to be imported
during the test run.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false