Use the error context API in espeak_ng_CompileMbrolaVoice.

src/espeak-ng.c

 				phonemes_separator = 0x200d; // ZWJ
 			break;
 		case 0x10e: // --compile-mbrola
+		{
 			espeak_ng_InitializePath(data_path);
-			return (espeak_ng_CompileMbrolaVoice(optarg2, stdout) == ENS_OK) ? EXIT_SUCCESS : EXIT_FAILURE;
+			espeak_ng_ERROR_CONTEXT context = NULL;
+			espeak_ng_STATUS result = espeak_ng_CompileMbrolaVoice(optarg2, stdout, &context);
+			if (result != ENS_OK) {
+				espeak_ng_PrintStatusCodeMessage(result, stderr, context);
+				espeak_ng_ClearErrorContext(&context);
+				return EXIT_FAILURE;
+			}
+			return EXIT_SUCCESS;
+		}
 		case 0x10f: // --compile-intonations
 			espeak_ng_InitializePath(data_path);
 			return (espeak_ng_CompileIntonation(stdout) == ENS_OK) ? EXIT_SUCCESS : EXIT_FAILURE;

src/include/espeak-ng/espeak_ng.h

 
 ESPEAK_NG_API espeak_ng_STATUS
 espeak_ng_CompileMbrolaVoice(const char *path,
-                             FILE *log);
+                             FILE *log,
+                             espeak_ng_ERROR_CONTEXT *context);
 
 ESPEAK_NG_API espeak_ng_STATUS
 espeak_ng_CompilePhonemeData(long rate,

src/libespeak-ng/compilembrola.c

 #include "speak_lib.h"
 #include "espeak_ng.h"
 
+#include "error.h"
 #include "phoneme.h"
 #include "speech.h"
 #include "synthesize.h"
 }
 
 #pragma GCC visibility push(default)
-espeak_ng_STATUS espeak_ng_CompileMbrolaVoice(const char *filepath, FILE *log)
+espeak_ng_STATUS espeak_ng_CompileMbrolaVoice(const char *filepath, FILE *log, espeak_ng_ERROR_CONTEXT *context)
 {
 	if (!log) log = stderr;
 
 	MBROLA_TAB data[N_PHONEME_TAB];
 
 	strcpy(buf, filepath);
-	if ((f_in = fopen(buf, "r")) == NULL) {
-		fprintf(log, "Can't read: %s\n", filepath);
-		return errno;
-	}
+	if ((f_in = fopen(buf, "r")) == NULL)
+		return create_file_error_context(context, errno, buf);
 
 	while (fgets(buf, sizeof(phoneme), f_in) != NULL) {
 		buf[sizeof(phoneme)-1] = 0;
 
 	strcpy(mbrola_voice, basename(filepath));
 	sprintf(buf, "%s/mbrola_ph/%s_phtrans", path_home, mbrola_voice);
-	if ((f_out = fopen(buf, "wb")) == NULL) {
-		fprintf(log, "Can't write to: %s\n", buf);
-		return errno;
-	}
+	if ((f_out = fopen(buf, "wb")) == NULL)
+		return create_file_error_context(context, errno, buf);
 
 	data[count].name = 0; // list terminator
 	Write4Bytes(f_out, mbrola_ctrl);

src/speak-ng.c

 				phonemes_separator = 0x200d; // ZWJ
 			break;
 		case 0x10e: // --compile-mbrola
+		{
 			espeak_ng_InitializePath(data_path);
-			return (espeak_ng_CompileMbrolaVoice(optarg2, stdout) == ENS_OK) ? EXIT_SUCCESS : EXIT_FAILURE;
+			espeak_ng_ERROR_CONTEXT context = NULL;
+			espeak_ng_STATUS result = espeak_ng_CompileMbrolaVoice(optarg2, stdout, &context);
+			if (result != ENS_OK) {
+				espeak_ng_PrintStatusCodeMessage(result, stderr, context);
+				espeak_ng_ClearErrorContext(&context);
+				return EXIT_FAILURE;
+			}
+			return EXIT_SUCCESS;
+		}
 		case 0x10f: // --compile-intonations
 			espeak_ng_InitializePath(data_path);
 			return (espeak_ng_CompileIntonation(stdout) == ENS_OK) ? EXIT_SUCCESS : EXIT_FAILURE;