use SigMFArchiveReader for fromfile()

[jacobagilbert]

Closes #244

Also cleans up SigMFFileError imports/usage.

[jacobagilbert]

@gmabey does this seem like a reasonable way to address 244? I think we have accumulated a bit of architectural debt in the python module and it we can discuss that in the future (there is a circular import issue here which is why the import is inline) but that can be done once we get a functional release up.

[gmabey]

Yes, looks very reasonable to me, although I have not yet actually tried it. And -- I appreciate those cleanups too.

[jacobagilbert]

Thanks @gmabey ill hold on this until you can give it a spin, doesnt need to be merged today or anything... shooting for release next week or week after, and this should probably be in there.

[gmabey]

I'm getting a Metadata in archive did not .validate()! that I didn't expect, but there's no detail. It looks like @jacobagilbert had that part commented out in #263.

Actually I've had that error pop up for a while, I just kept hoping it would go away when those validate PRs were finally merged. Is anyone else seeing that message?

[jacobagilbert]

Ah yea i should probably remove those lines here. validate() no longer returns a bool, it throws an exception if it fails so that check just prints that line for no reason. Thats a bug.

Edit: Give it a shot now.

[jacobagilbert]

Concurrence on the call today, merging.