Can't get Script Filter to find the pinboard.py file from the tutorial

I've been unable to replicate the pinboard example from the tutorial. The code runs fine when run from the command line, but when triggered via Alfred no list items show up. Per the debugger it looks like Alfred can't find the script:
```
[21:38:51.942] Logging Started...
[21:40:04.764] File namer[Snippet] Processing complete
[21:40:04.770] File namer[Snippet] Passing output '' to Script Filter
[21:40:04.788] File namer[Script Filter] Queuing argument '(null)'
[21:40:04.877] File namer[Script Filter] Script with argv '(null)' finished
[21:40:04.880] ERROR: File namer[Script Filter] Code 2: /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: can't open file 'pinboard.py': [Errno 2] No such file or directory
```
This is when the Script Filter is configured with `/bin/bash` and
```
python pinboard.py
```
The script is located in the workflow directory, and if I pass in a complete pathname, it works.

Is there something special needed for the Script Filter to launch in the workflow directory and thus be able to use filenames relative to that directory?