Add warning/info for missing Python modules in examples
|Assignee:||Tom Rondeau||% Done:||
Many examples rely on other Python modules that are not included as dependencies in GNU Radio, such as the gr-trellis and the PFB examples. The required Python modules are usually scipy or matplotlib. These are not dependencies we care to check for during configuration/build.
At least some of the PFB examples check for these modules and then print out a message about the missing module and where to get it. Make sure all examples that call these external Python dependencies provide useful messages and gracefully fail.