import datatlad only when running download_dataset()

[samuelgarcia]

This remove the systematic import od datalad which can be annoying in notebook for some version because it trigger lot of errors.
datalad will be now imported on demand only.

[pep8speaks]

Hello @samuelgarcia! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file neo/test/iotest/common_io_test.py:

Line 41:1: E722 do not use bare 'except'

• In the file neo/test/rawiotest/common_rawio_test.py:

Line 33:1: E722 do not use bare 'except'

• In the file neo/test/rawiotest/tools.py:

Line 18:5: E722 do not use bare 'except'

Comment last updated at 2022-07-01 12:42:48 UTC

[JuliaSprenger]

Hi Samuel, I am a bit confused as in the title it sounds like you only want to import datalad in download_dataset, but your changes try to import datalad also in multiple other modules.
Maybe a better approach would be to try to download the dataset and catch the datalad missing exception when this fails?

[samuelgarcia]

the try .. except is only at in subfolder tests.
The only real place is in the function.

[JuliaSprenger]

Ok, I will merge this as soon as the tests are completed.