Improve ServiceError reporting

rust/agama-lib/src/error.rs

@@ -6,9 +6,9 @@ use zbus;
 
 #[derive(Error, Debug)]
 pub enum ServiceError {
- #[error("D-Bus service error")]
+ #[error("D-Bus service error: {0}")]
  DBus(#[from] zbus::Error),
- #[error("Could not connect to Agama bus at '{0}'")]
+ #[error("Could not connect to Agama bus at '{0}': {1}")]
  DBusConnectionError(String, #[source] zbus::Error),
  // it's fine to say only "Error" because the original
  // specific error will be printed too
@@ -20,7 +20,7 @@ pub enum ServiceError {
  FailedRegistration(String),
  #[error("Failed to find these patterns: {0:?}")]
  UnknownPatterns(Vec<String>),
- #[error("Error: {0}")]
+ #[error("Could not perform action '{0}'")]
  UnsuccessfulAction(String),
 }