fix crash when doing debugging output

[phkehl]

Crashes hard when trying to do get() on str.
I tried to work out what your intention here was and fix it accordingly.
I may have understood it totally wrong. My Python-foo isn't terribly strong.
With this change it does output something, and it doesn't crash.

[Farfar]

Thanks! Never noticed this in current testing environment since the error is handled. The debug log is there to help determine if get/post requests are actually supported for given vehicle. Nothing that really impacts the use of the library at the moment.