add a bunch more readthedocs from wiki

readthedocs/extra/troubleshooting/rpc-errors.rst

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+==========
+RPC Errors
+==========
+
+RPC stands for Remote Procedure Call, and when Telethon raises an
+``RPCError``, it’s most likely because you have invoked some of the API
+methods incorrectly (wrong parameters, wrong permissions, or even
+something went wrong on Telegram’s server). The most common are:
+
+-  ``FloodError`` (420), the same request was repeated many times. Must
+   wait ``.seconds``.
+-  ``SessionPasswordNeededError``, if you have setup two-steps
+   verification on Telegram.
+-  ``CdnFileTamperedError``, if the media you were trying to download
+   from a CDN has been altered.
+-  ``ChatAdminRequiredError``, you don’t have permissions to perform
+   said operation on a chat or channel. Try avoiding filters, i.e. when
+   searching messages.
+
+The generic classes for different error codes are: \* ``InvalidDCError``
+(303), the request must be repeated on another DC. \*
+``BadRequestError`` (400), the request contained errors. \*
+``UnauthorizedError`` (401), the user is not authorized yet. \*
+``ForbiddenError`` (403), privacy violation error. \* ``NotFoundError``
+(404), make sure you’re invoking ``Request``\ ’s!
+
+If the error is not recognised, it will only be an ``RPCError``.