docs(python): document trezorlib exception classes

python/src/trezorlib/exceptions.py

@@ -24,10 +24,15 @@ if TYPE_CHECKING:
 
 
 class TrezorException(Exception):
-    pass
+    """General Trezor exception."""
 
 
 class TrezorFailure(TrezorException):
+    """Failure received over the wire from Trezor.
+
+    Corresponds to a `Failure` protobuf message.
+    """
+
     def __init__(self, failure: Failure) -> None:
         self.failure = failure
         self.code = failure.code
@@ -49,18 +54,33 @@ class TrezorFailure(TrezorException):
 
 
 class PinException(TrezorException):
-    pass
+    """PIN operation has failed.
+
+    This exception is only raised on Trezor Model One. It indicates to the caller that
+    the Trezor rejected the PIN entered via host-side matrix keyboard.
+    """
 
 
 class Cancelled(TrezorException):
-    pass
+    """Action was cancelled.
+
+    Cancellation can be either received from Trezor or caused by the library, typically
+    in response to user action."""
 
 
 class OutdatedFirmwareError(TrezorException):
-    pass
+    """Trezor firmware is too old.
+
+    Raised when interfacing with a Trezor whose firmware version is no longer supported
+    by current library version."""
 
 
 class UnexpectedMessageError(TrezorException):
+    """Unexpected message received from Trezor.
+
+    Raised when the library receives a response from Trezor that does not match the
+    previous request."""
+
     def __init__(self, expected: type[MessageType], actual: MessageType) -> None:
         self.expected = expected
         self.actual = actual