LGTM.com - false positive - unused import in `try` statement

**Description of the false positive**

`Unused import` reported, when the import is in a `try` statement to check the availability of a package, which determines the tests to be run afterwards. May be good if imports in a `try` statement are excempt from such a report.

**URL to the alert on the project page on LGTM.com**

https://lgtm.com/projects/g/hyperspy/hyperspy/snapshot/508d6caf0efc5c0a258c67f5c2ecab8a977c413e/files/hyperspy/conftest.py#x4aef4cf8f643dffd:1