Debugging a failed Dataflow job

[Gareth Western]

I'm having trouble running my pipeline using the dataflow runner. The 
job is submitted successfully:

Dataflow SDK version: 0.4.0
Submitted job: 2017-01-23_12_17_20-13351949104581541182
but in the Dataflow console it simply says " workflow failed". I can't 
seem to find any more details regarding the cause of the failure. Where 
should I be looking?