Description: Takes the output from an udm command and checks for the return code (must be a single number in the last line). If the return code is non-zero, all lines above the last line are treated as error message and written to $errorMessage.
Parameter:
ret: The complete message block with return code (must be a single number in the last line)
errorMessage: The variable, the error message may be written to.
Returns:
true, if the udm command returned a success return code (0), otherwise false.
