downgrade severity of the exception raised when there is no evt2 file.

Author: javierggt

astromon/observation.py

@@ -531,7 +531,7 @@ def filter_events(self, radius=180, psfratio=1):  # radius in arcsec
         try:
             evt = list((self.workdir / 'primary').glob('*evt2.fits*'))[0]
         except Exception:
-            raise Exception(f'evt2 file not found   ') from None
+            raise SkippedWithWarning(f'evt2 file not found') from None
 
         evt2 = str(evt).replace('evt2', 'evt2_filtered')