fix pyicu import to suppress warnings

[brian-from-quantrocket]

Newer versions of pyicu should be imported as

import icu 

whereas

import PyICU 

will print a warning.

This fix uses the preferred import if available and otherwise falls back to the older name.

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This change is 

[bear]

Reviewed 1 of 1 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[bear]

Thanks for the fix