isPassable = specimen => {
  try {
    // In fact, it never returns undefined. It either returns a
    // string or throws.
    return passStyleOf(specimen) !== undefined;
  } catch (_) {
    return false;
  }
}
Is `specimen` Passable? This returns true iff `passStyleOf(specimen)`
returns a string. This returns `false` iff `passStyleOf(specimen)` throws.
Under no normal circumstance should `isPassable(specimen)` throw.

TODO Deprecate and ultimately delete @agoric/base-zone's `isPassable' in
favor of this one.
See https://github.com/endojs/endo/issues/2096

TODO implement an isPassable that does not rely on try/catch.
This implementation is just a standin until then.
See https://github.com/endojs/endo/issues/2096

@param {any} specimen
@returns {specimen is Passable}