Fermipy independence

[deividribeiro]

If fermipy is not in environment, the try/catch block fails, but the error message points to logging rather than logger.

vtspy/vtspy/analysis/fermi_analysis.py

Line 29 in bd6ced3

logging.warning("Fermitools is not installed. Any Fermi-LAT related analysis cannot be performed.")

Additionally, if this is the case, the following import lines

import fermipy.wcs_utils as wcs_utils
import fermipy.utils as fermi_utils

also fail, and should be moved inside the try/catch block.