codal_port: Enable uerrno module to get nicer OSError exceptions.

If known, the symbolic name of the OSError is now printed as part of the
exception message.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/microbit_uart.c

@@ -144,7 +144,7 @@ STATIC mp_uint_t microbit_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t si
 
     // check there is at least 1 char available
     if (!mp_hal_stdio_poll(MP_STREAM_POLL_RD)) {
-        *errcode = EAGAIN;
+        *errcode = MP_EAGAIN;
         return MP_STREAM_ERROR;
     }
 

src/codal_port/mpconfigport.h

@@ -61,6 +61,7 @@
 #define MICROPY_MODULE_WEAK_LINKS               (1)
 #define MICROPY_MODULE_FROZEN_MPY               (1)
 #define MICROPY_QSTR_EXTRA_POOL                 mp_qstr_frozen_const_pool
+#define MICROPY_USE_INTERNAL_ERRNO              (1)
 #define MICROPY_ENABLE_SCHEDULER                (1)
 
 // Fine control over Python builtins, classes, modules, etc
@@ -77,6 +78,7 @@
 #define MICROPY_PY_SYS_PLATFORM                 "microbit"
 
 // Extended modules
+#define MICROPY_PY_UERRNO                       (1)
 #define MICROPY_PY_UTIME_MP_HAL                 (1)
 #define MICROPY_PY_URANDOM                      (1)
 #define MICROPY_PY_URANDOM_EXTRA_FUNCS          (1)