tohil::eval aborts when trying to convert certain type(s) from Python to Tcl

Reduce reproduction of some code from pyman that triggers this:
```tcl
package require tohil
tohil::import inspect
puts [tohil::eval {inspect.getmembers(inspect)}]
```
This causes an abort in `pyObjToTcl()` because `_pyObjToTcl()` is returning NULL. Must be some Python data type in the `inspect` module that we're not converting right.