limit semantic_version to <=2.6

[nden]

No description provided.

[olebole]

Is there a specific reason for that?
In Debian,we have now now semantic_version 2.8.2,which makes it impossible to create the Debian package here.

[nden]

Well, in general, it should be possible to relax. The reason was that at the time of the previous asdf release semantic_versioning changed rapidly in a few days - there were four pypi releases in two days. SpecItem is deprecated in these and deprecation warnings raise an error in astropy. So it was a stop-gap measure. And we haven't had time to figure out what replaces SpecItem. I guess another stop-gap measure would be to disallow 3.x releases and ignore the DeprecationWarning.

[olebole]

Since asdf is used by other packages (like sunpy) , it should not restrict the versions of its dependencies by itself too much, otherwise there is the danger of conflicts. And SpecItem is mentioned being private.
Isn't SimpleSpec (or BaseSpec) the right replacement here?

[nden]

Perhaps. I'm not familiar with the reasons SpecItem was used. I'll take a look. Thanks for the pointer.