Try setting JAVA_HOME, JDK_HOME, PYTHON_HOME and the PATH for python at the environmental settings of your pc (if you use windows). There could be a confusion between various java and python versions present at your pc or they could be not visible from the command line you are using.
Try to use the conda command line instead of the windows one. At least for me that worked. I used OSGeo instead of conda (I don’t have Anaconda installed), but from the OSGeo command line I managed to install snappy successfully while from the windows command line I had similar errors like yours.
I’m not sure whether this will fix your problem but you can try.