You can colorize Python messages in iTerm by adding triggers to your profile.
iTerm > Settings > Profiles > Triggers > Edit
Highlight Text - Traceback calls:
Traceback([\s\S]*)
Highlight Text - line and number:
line [\d]*
Highlight Text - errors:
(BaseException|Exception|StandardError|ArithmeticError|BufferError|LookupError|EnvironmentError|AssertionError|AttributeError|EOFError|FloatingPointError|GeneratorExit|IOError|ImportError|IndexError|KeyError|KeyboardInterrupt|MemoryError|NameError|NotImplementedError|OSError|OverflowError|ReferenceError|RuntimeError|StopIteration|SyntaxError|IndentationError|TabError|SystemError|SystemExit|TypeError|UnboundLocalError|UnicodeError|UnicodeEncodeError|UnicodeDecodeError|UnicodeTranslateError|ValueError|VMSError|WindowsError|ZeroDivisionError|Warning|UserWarning|DeprecationWarning|PendingDeprecationWarning|SyntaxWarning|RuntimeWarning|FutureWarning|ImportWarning|UnicodeWarning)(.*)