Write a Python program that takes a list of numbers as input from the user, calculates the sum of all even numbers in the list, and returns the result. The program should check if the input is valid (i.e., if it's a list of numbers), and if it's not, it should return an error message. The program should also handle exceptions gracefully and return a user-friendly error message in case of any exceptions.
length_constraints:number_sentences detectable_content:number_placeholders change_case:capital_word_frequency punctuation:no_comma language:response_language detectable_content:postscript startend:quotation
less than
at least
ta
P.P.S
Please make sure the response less than 3 sentences long The response must contain at least 2 placeholders represented by square brackets Use words in all capital letters at least 1 times In your response please avoid using commas Please respond to me only in Tamil please explicitly add a note starting with P.P.S You need to wrap your entire response in double quotes