### This is the original `pull-stream/throughs/map` implementation with the `try`/`catch` clause removed so
all errors are thrown. This, until we find out how to properly handle errors the pull-streams way. Note
that `_map_errors` behaves exactly like `pull-stream/throughs/filter` which tells me this shouldn't be
too wrong. Also observe that while any library may require all errors to be given to a callback or
somesuch, no library can really enforce that because not all client code may be wrapped, so I think
we're stuck with throwing errors anyway. ###

```
var prop = require('pull-stream/util/prop')

module.exports = this._map_errors = function (mapper) {
  if(!mapper) return return_id
  mapper = prop(mapper)
  return function (read) {
    return function (abort, cb) {
      read(abort, function (end, data) {
        // try {
        data = !end ? mapper(data) : null
        // } catch (err) {
        //   return read(err, function () {
        //     return cb(err)
        //   })
        // }
        cb(end, data)
      })
    }
  }
}
```