Fixed SyntaxWarning: "is" with a literal.
Fixed SyntaxWarning: "is" with a literal.

Code would throw a syntax warning, as included below.

```/Users/tijme/Workspace/Tools/pub-dpat/./resources/dpat.py:520: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if ((response is "") or (strtobool(response))):```
clr2of8/DPAT