Remove owned String from CustomError.

This is a 15% performance improvement.

src/parser/in_buffer_settings.rs

@@ -102,7 +102,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
     }) {
         let (_, (in_progress_words, complete_words)) =
             todo_keywords(kw.value).map_err(|err| match err {
-                nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+                nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
                 nom::Err::Error(e) => e,
                 nom::Err::Failure(e) => e,
             })?;
@@ -123,7 +123,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
             kw.value,
         )
         .map_err(|err: nom::Err<_>| match err {
-            nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+            nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
             nom::Err::Error(e) => e,
             nom::Err::Failure(e) => e,
         })?;
@@ -141,7 +141,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
         .filter(|kw| kw.key.eq_ignore_ascii_case("link"))
     {
         let (_, (link_key, link_value)) = link_template(kw.value).map_err(|err| match err {
-            nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+            nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
             nom::Err::Error(e) => e,
             nom::Err::Failure(e) => e,
         })?;