Move the Navigator startup out of exception handling.
Move the Navigator startup out of exception handling.

Otherwise, any other traceback would be prefixed with:

Traceback (most recent call last):
  File "weasyprint/navigator.py", line 160, in run
    from werkzeug.serving import run_simple
ImportError: No module named werkzeug.serving

During handling of the above exception, another exception occurred:

jasco/WeasyPrint,marclaporte/WeasyPrint,Kozea/WeasyPrint,prepare/TestWeasyPrint,jasco/WeasyPrint,andrewleech/WeasyPrint,andrewleech/WeasyPrint,Kozea/WeasyPrint,prepare/TestWeasyPrint,marclaporte/WeasyPrint