cli: Avoid empty error message (#4230)

If the `dev` command encounters an HTTP error when fetching module logs,
it relies on the server to also send some error description in the
response body.

That isn't always the case, so default to the status code + canonical
reason phrase

# Expected complexity level and risk

1

# Testing

n/a

Author: kim

crates/cli/src/subcommands/dev.rs

@@ -61,7 +61,7 @@ pub fn cli() -> Command {
                 .help("The path to the module bindings directory relative to the project directory, defaults to `<project-path>/src/module_bindings`"),
         )
         // NOTE: All server templates must have their server code in `spacetimedb/` directory
-        // This is not a requirement in general, but is a requirement for all templates 
+        // This is not a requirement in general, but is a requirement for all templates
         // i.e. `spacetime dev` is valid on non-templates.
         .arg(
             Arg::new("module-project-path")
@@ -620,7 +620,13 @@ async fn stream_logs(
 
     let status = res.status();
     if status.is_client_error() || status.is_server_error() {
-        let err = res.text().await?;
+        let mut err = res.text().await?;
+        // The server doesn't always send an error description in the response
+        // body (maybe it should), so default to status code + canonical reason
+        // phrase (e.g. "502 Bad Gateway").
+        if err.is_empty() {
+            err = format!("{status}");
+        }
         anyhow::bail!(err)
     }