File "/Users/glyph/.emacs.d/elpa/highlight2clipboard-20151020.1840/bin/highlight2clipboard-osx.py", line 58
print "Add HTML text to pasteboard"
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print("Add HTML text to pasteboard")?
python3 is installed along with the xcode command line tools, so you could use that, but pyobjc (ideally, just, pyobjc-framework-Cocoa so as not to drag in a million unnecessary frameworks) also will need to be installed via pip in that virtualenv.