* handle executor should_panic test better
* Revert "reduce should panic, due to extended error messages"
This reverts commit c0805940184a62cd9302603ad911c3591e70a60c.
* remove excessive constraints
* remove duplicate documentation messages for error variants
* reduce T: constraints to the abs minimum
* whoops
* fewer bounds again
Co-authored-by: Bernhard Schuster <bernhard@parity.io>