Fix Markup object repr in debug console

[ChrisDryden]

The console was assuming that all objects of string type would only return a string in repr(). This meant that objects that gave response of its object type along with a string in repr were breaking parts of the code that removed the parenthesis. By verifying that an object is a string type instead of a string instance this bug can be fixed.

Fixes #1129

[ChrisDryden]

This fixes issue #1129

[ThiefMaster]

LGTM once you remove that trailing whitespace

[ThiefMaster]

Also, please amend the commit message to be more concise - first line shouldn't be more than 51 chars, and certainly so long that github truncates it. My suggestion would be something like "Fix Markup object repr in debugger"

[davidism]

I'd like to experiment a little more before merging this. This fix works, but now it ignores subclasses of str that still have the standard repr.

[davidism]

Demo of some alternatives in #1397

addressed

[davidism]

I ended up committing a different fix that still allows subclasses. Thanks for working on this during the sprints, just digging in and figuring out where things were happening and why was really helpful.

New version collapses the repr rather than slicing the original object, then only adds subclass info if the repr looks like the standard string repr.