private String getNoFetcherMsg(String fetcherName) {
        StringBuilder sb = new StringBuilder();
        sb.append("Fetcher '").append(fetcherName).append("'");
        sb.append(" not found.");
        sb.append("\nThe configured FetcherManager supports:");
        int i = 0;
        for (String f : fetcherManager.getSupported()) {
            if (i++ > 0) {
                sb.append(", ");
            }
            sb.append(f);
        }
        return sb.toString();
    }
returns stack trace if there was a container exception or empty string
if there was no stacktrace

@param t
@param metadataList
@return
tika-core/src/main/java/org/apache/tika/pipes/PipesServer.java