private String getNoEmitterMsg(String emitterName) {
        StringBuilder sb = new StringBuilder();
        sb.append("Emitter '").append(emitterName).append("'");
        sb.append(" not found.");
        sb.append("\nThe configured emitterManager supports:");
        int i = 0;
        for (String e : emitterManager.getSupported()) {
            if (i++ > 0) {
                sb.append(", ");
            }
            sb.append(e);
        }
        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