Improve error handling when calling ck2cti and ctml_writer
Improve error handling when calling ck2cti and ctml_writer

Only look for modules in the new location (inside the cantera package), and
print the path if they aren't found, to aid in debugging.

Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera