improve error messages when creating invalid HoppingKinds

Closes #147 (closed).

Also uncovered an invalid HoppingKind creation in the tests!

assigned to @cwg

Looks perfect, thanks.

Just curious: is it better to write except Exception: rather than except:?

Isn't it right that if we catch a generic error, we must also reraise it. For example right now the same error message would be shown if the arguments aren't site families at all (e.g. lists of site families, builders, systems, numpy arrays, etc).

@anton-akhmerov you suggest that we use raise X from Y?

Just curious: is it better to write except Exception: rather than except:?

The latter (bare) except catches any BaseException, which includes KeyboardInterrupt and MemoryError. A bare except is usually considered a code smell.

For example right now the same error message would be shown if the arguments aren't site families at all

@anton-akhmerov not true; there is an ensure_isinstance check in the preceding lines.

added 7 commits

• 9fda0266...4faf0584 - 4 commits from branch kwant:stable
• 9b205b5a - add test that defines failure modes of HoppingKinds
• c53f7a6d - add compatibility check between site families and delta in HoppingKinds
• b9403d1e - fix broken HoppingKind test

Compare with previous version

merged

mentioned in commit 732a1695