message: remove bare unwrap
diff: @@ -22,6 +22,7 @@ use wrangler::settings::toml::TargetType;
  use wrangler::terminal::message::{Message, Output, StdOut};
  use wrangler::terminal::{emoji, interactive, styles};
  use wrangler::version::background_check_for_updates;
  +use futures_util::TryStreamExt;
  fn main() -> Result<(), ExitFailure> {
  env_logger::init();
  @@ -1054,10 +1055,14 @@ fn run() -> Result<(), failure::Error> {
  let expiration_ttl = put_key_matches
  .value_of("expiration-ttl")
  .map(|t| t.to_string());
  - let metadata = put_key_matches
  + let metadata: Option<serde_json::Value> = put_key_matches
  .value_of("metadata")
  - .map(serde_json::from_str)
  - .map(Result::unwrap); // success is guaranteed in the argument's `validator` call
  + .map(|s| {
  + match serde_json::from_str::<serde_json::Value>(s) {
  + Ok(v) => v,
  + Err(e) => failure::bail!("--metadata is not valid JSON: {}", e),
  + }
  + });
  let kv_metadata = KVMetaData {
  namespace_id,
  key,
  