unix: OSError's args[0] should be errno numeric value.

Well, Python3 also defines an attribute for that, but that's bloat.

unix/file.c

@@ -106,7 +106,7 @@ STATIC mp_obj_t fdfile_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
 
     int fd = open(fname, mode, 0644);
     if (fd == -1) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", errno));
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }
     return fdfile_new(fd);
 }

unix/modffi.c

@@ -145,7 +145,7 @@ STATIC mp_obj_t ffimod_func(uint n_args, const mp_obj_t *args) {
 
     void *sym = dlsym(self->handle, symname);
     if (sym == NULL) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", errno));
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }
     int nparams = MP_OBJ_SMALL_INT_VALUE(mp_obj_len_maybe(args[3]));
     mp_obj_ffifunc_t *o = m_new_obj_var(mp_obj_ffifunc_t, ffi_type*, nparams);
@@ -219,7 +219,7 @@ STATIC mp_obj_t ffimod_var(mp_obj_t self_in, mp_obj_t vartype_in, mp_obj_t symna
 
     void *sym = dlsym(self->handle, symname);
     if (sym == NULL) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", errno));
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }
     mp_obj_ffivar_t *o = m_new_obj(mp_obj_ffivar_t);
     o->base.type = &ffivar_type;
@@ -235,7 +235,7 @@ STATIC mp_obj_t ffimod_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     void *mod = dlopen(fname, RTLD_NOW | RTLD_LOCAL);
 
     if (mod == NULL) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", errno));
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }
     mp_obj_ffimod_t *o = m_new_obj(mp_obj_ffimod_t);
     o->base.type = type_in;

unix/modsocket.c

@@ -33,7 +33,7 @@ STATIC const mp_obj_type_t microsocket_type;
 // Helper functions
 #define RAISE_ERRNO(err_flag, error_val) \
     { if (err_flag == -1) \
-        { nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", error_val)); } }
+        { nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error_val))); } }
 
 STATIC mp_obj_socket_t *socket_new(int fd) {
     mp_obj_socket_t *o = m_new_obj(mp_obj_socket_t);