logging: remove useless error string in Level conversion

The error message should be constructed by the caller if needed,
and explain the context of the error in more abstract terms, not
such low-level wrapper implementation details.

Author: wprzytula

scylla-rust-wrapper/src/logging.rs

@@ -54,7 +54,7 @@ impl From<Level> for CassLogLevel {
 }
 
 impl TryFrom<CassLogLevel> for Level {
-    type Error = String;
+    type Error = ();
 
     fn try_from(log_level: CassLogLevel) -> Result<Self, Self::Error> {
         let level = match log_level {
@@ -64,7 +64,7 @@ impl TryFrom<CassLogLevel> for Level {
             CassLogLevel::CASS_LOG_WARN => Level::WARN,
             CassLogLevel::CASS_LOG_ERROR => Level::ERROR,
             CassLogLevel::CASS_LOG_CRITICAL => Level::ERROR,
-            _ => return Err("Error while converting CassLogLevel to Level".to_string()),
+            _ => return Err(()),
         };
 
         Ok(level)