Implement proper error messages for duplicate identities

[kwannoel]

In GitLab by @kwanzknoel on Sep 18, 2021, 04:35

Duplicate identities error out without explicitly stating the reason.

For instance if alice is already added before, and we add her again:

> $ ./glow generate-identity -E pet -N alice                                                                                                                                                    
Glow 0.3.1-4-g7ead4e9 on Gerbil-ethereum v0.0-344-g266204c, Gerbil-persist v0.0-19-g75d4c45, Gerbil-crypto v0.0-16-g4c7c4a8, Gerbil-poo v0.0-96-g8ab28ef, Gerbil-utils v0.2-134-g124e025, Gerbil v0.16-192-gfa9537be, Gambit 4.9.3-1447-gc0753ff1
In thread primordial:
0  std/db/dbi#sql-exec                                                                                                                                     (__method309168 _stmt257591_)
        _stmt257591_ == '#<sqlite-statement #105>
1  mukn/glow/contacts/db#insert-identities                                     
2  mukn/glow/contacts/db#add-identity                                          
3  mukn/glow/cli/identities#add-identity__%                                    
4  ##dynamic-env-bind                                                          
5  ##call-with-values                                                          
6  clan/exit#call-print-exit                                                   
7  ##dynamic-env-bind                                                          
8  ##start-main                                                                
9  ##kernel-handlers                                                           
*** ERROR IN std/db/dbi#sql-exec -- sqlite-exec: [sql-error] SQLite error: constraint failed
--- irritants: 19 

We should display a more helpful error message.

[kwannoel]

In GitLab by @kwanzknoel on Sep 18, 2021, 04:35

changed title from {-Handle-} duplicate identities to {+Implement proper error messages for+} duplicate identities