Wrong std::string overload called when given numpy.ndarray argument

[pschella]

When an overload is present that takes a std::string argument, this overload is also (wrongly) called when given a numpy.ndarray.

See attached unit test patch to latest master.
broken_overload.txt

[dean0x7d]

Looks like it only affects Python 2. PyUnicode_FromObject might be a bit too permissive and accepts ndarray via the buffer protocol:

https://docs.python.org/2.7/c-api/unicode.html#c.PyUnicode_FromObject
String and other char buffer compatible objects are decoded according to the given encoding

@jagerman Perhaps an additional PyString_Check is needed for Python 2?

[pschella]

Any chance we can get a new point release with the fix for this, #597, #688 and potentially other recent fixes?