Function error_chain_message 

pub fn error_chain_message(err: &(dyn Error + 'static)) -> String

Render err followed by every error in its source() chain, joined by ": ".

reqwest’s own Display prints only its outermost frame (e.g. “error sending request for url (…)”); the cause it wraps — notably a SafeDnsResolver SSRF refusal — lives in the source() chain and would otherwise be silently dropped.