fix(verify): improve error message for unsupported chain in Etherscan verifier (#12685)

* Update provider.rs

* Update verify.rs

* clippy

* clippy

---------

Co-authored-by: grandizzy <[email protected]>

Author: DeVikingMark

crates/forge/tests/cli/verify.rs

@@ -348,7 +348,7 @@ Error: No verifier URL specified for verifier blockscout
         .assert_failure()
         .stderr_eq(str![[r#"
 Error: No known Etherscan API URL for chain `4202`. To fix this, please:
-1. Specify a `url` 
+1. Specify a `url` when using Etherscan verifier
 2. Verify the chain `4202` is correct
 
 "#]]);

crates/verify/src/provider.rs

@@ -190,7 +190,10 @@ impl VerificationProviderType {
             if let Some(chain) = chain
                 && chain.etherscan_urls().is_none()
             {
-                eyre::bail!(EtherscanConfigError::UnknownChain(String::new(), chain))
+                eyre::bail!(EtherscanConfigError::UnknownChain(
+                    "when using Etherscan verifier".to_string(),
+                    chain
+                ))
             }
             if !has_key {
                 eyre::bail!("ETHERSCAN_API_KEY must be set to use Etherscan as a verifier")