Python 2.7 basestring abstract type is removed in python 3.

[David Platten]

Need to use str instead - see https://docs.python.org/3.0/whatsnew/3.0.html#text-vs-data-instead-of-unicode-vs-8-bit. This affects the chart code.

[Ed McDonagh]

@David Platten - I think this might all be dealt with. Do you agree?

[David Platten]

Yes, agreed.

[Ed McDonagh]

Adding ref #790 to changes. Closes #790

→ <<cset ccabfb9a4de6>>

[Ed McDonagh]

Adding ref #790 to changes. Closes #790

→ <<cset ccabfb9a4de6>>