PyLaunchy is an embedded Python environment, which means you have no console output. In general, there are two ways to debug:
Logging with print statements or with the Python logging module. For example, the following script will print a line which can be seen in plugins/python/stdout.txt:
import launchy
print "I was printed from python!"
Using Winpdb and Embedded Debugging. For example, the following script will halt Launchy and wait for Winpdb to attach:
import rpdb2; rpdb2.start_embedded_debugger("mypassword")
import launchy