In python 2.6 floating numbers in a trait_definition are not always nicely rendered

Numbers in a trait definition that cannot be exactly represented in floating point representation will not be nicely printed when using python 2.6

The underline issue is that the astor library that is used to convert the Python ast to a nicely formated string uses the `repr` which in python 2.6 can sometimes return unplesent results (https://docs.python.org/2.6/tutorial/floatingpoint.html)