I installed theano but when I try to use it I got this error:

WARNING (theano.configdefaults): g++ not detected! Theano will be unable to execute 
   optimized C-implementations (for both CPU and GPU) and will default to Python 
   implementations. Performance will be severely degraded.

I installed g++, and put the correct path in the environment variables, so it is like theano does not detect it.
Does anyone know how to solve the problem or which may be the cause?
This is the error that I experienced in my mac running jupyter notebook with a python 3.5 kernal hope this helps someone, i am sure rggir is well sorted at this stage :) 
Error
Using Theano backend.
WARNING (theano.configdefaults): g++ not detected ! Theano will be unable to execute optimized C-implementations (for both CPU and GPU) and will default to Python implementations. Performance will be severely degraded. To remove this warning, set Theano flags cxx to an empty string.
Cause
update of XCode (g++ compiler) without accepting terms and conditions, this was pointed out above thanks Emiel
Resolution:

type g++ --version in the mac terminal
"Agreeing to the Xcode/iOS license requires admin privileges, please re-run as root via sudo." is output as an error
launch Xcode and accept terms and conditions
return g++ --version in the terminal
Something similar to the following will be returned to show that Xcode has been fully installed and g++ is now available to keras


Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Restart you machine… I am sure there are some more complicated steps that someone smarter than me can add here to make this faster
Run the model.fit function of the keras application which should run faster now … win!
theano g++ not detected