feat(Ubiquitous/RT_Thread): port micropython on RT-Thread for aiit-board

Ubiquitous/RT_Thread/micropython/docs/std-librarys/uerrno.md

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+## **uerrno** – 系统错误码模块
+
+`uerrno` 模块提供了标准的 errno 系统符号，每个符号都有对应的整数值。
+
+### 示例
+
+```python
+try:
+    uos.mkdir("my_dir")
+except OSError as exc:
+    if exc.args[0] == uerrno.EEXIST:
+        print("Directory already exists")
+uerrno.errorcode
+Dictionary mapping numeric error codes to strings with symbolic error code (see above):
+
+>>> print(uerrno.errorcode[uerrno.EEXIST])
+EEXIST
+```
+
+更多内容可参考 [uerrno](http://docs.micropython.org/en/latest/pyboard/library/uerrno.html) 。