PythonLayer takes parameters by string

[shelhamer]

Cherry-picking of the PythonLayer string parameter from #2001 by @tnarihi to give PythonLayer a param_str member for passing parameters through the python_param proto message.

This is a simple change in itself that leaves the choice of what and how to parameterize open.
There is no automatic eval

[shelhamer]

@philkr have you adapted this test to Python 3 already?

[philkr]

NamedTemporaryFile is created with mode='w+b' by default, which in python3 is a buffer, not a string. To fix this just call NamedTemporaryFile(mode='w+', delete=False).

[philkr]

The python3 error is easy to fix (see above). I have no idea why python2 fails on those warnings...

[tnarihi]

@shelhamer @philkr Thank you so much for taking care of my previous PR! Other than this, I still have a bunch of PRs for python that are not finished. If I need to update and polish them, please let me know.

[tnarihi]

According to this post in Stack Overflow, maybe we have to include Python.h first, which means we have to put include of boost/python.hpp first in tools/caffe.cpp. But I am not sure why this warning suddenly came out in this PR.

[philkr]

I think ac6d4b6 broke it. It seems to be broken for any PR based on the current master. ac6d4b6 introduced an additional include in caffe.cpp.

[shelhamer]

Hmm, the branch CI had passed but this is an issue. I'll try to fix it shortly.

[shelhamer]

@jeffdonahue @longjon does anybody have a favorite name or is param_str_ fine?

[jeffdonahue]

I think param_str is fine. It could also just be called param or arg since the str is a little redundant with the protobuf type, but I could also see how it might be a useful hint to have the str annotation when parsing in Python.

[shelhamer]

I changed the name of the property to param_str on the Python side and simplified the test to just check multiplication by the param_str value. @longjon take a look and merge if you like it.

[longjon]

Could we be consistent with single-quotes here?

[longjon]

Looks good except as noted.

[shelhamer]

Thanks for the glance @longjon. Fixed and merging.