trycatch() showing warning at end of pipeline

[msleckman]

trycatch() for target p1_nwis_sites returning the message pasted together underneath designated target.
e.g.

• built branch p1_nwis_sites_777dad85
• start branch p1_nwis_sites_db2a2fcc
Found invalid geometry, attempting to fix.
Spherical geometry (s2) switched off
Spherical geometry (s2) switched on
error - No gages found in huc8 16030009

But also get the warning that is baked into get_nwis() at end of target build which is not informative.

Warning messages:
1: No gages found in this AOI. 
2: No gages found in this AOI. 
3: No gages found in this AOI. 

First attempt to improve this found in my branch msleckman/saline_lakes/sw_pulls and to catch the warning.

• Later update: to show huc8 ids without nwis sites at end of build as a summary such that this sort of message No gages found in huc8 16030009 appears at end.