python3Packages.gpgme: enable python3 version

when calling python3Packages.gpgme, it was still picking python2.
Changed withPython into pythonSupport since it's the convention.

I had to enable ncurses too because of this error when configuring:

configure:19978: checking python extra libraries
configure:19985: result: -lpthread -ldl -lcrypt -lncurses -lutil -lm
configure:19992: checking python extra linking flags
configure:19999: result: -Xlinker -export-dynamic
configure:20006: checking consistency of all components of python development environment
configure:20032: gcc -o conftest -g -O2  -I/nix/store/hy65mn4wjswqih75gfr6g4q3xgqdm325-python3-3.6.6/include/python3.6m  conftest.c  -L/nix/store/hy65mn4wjswqih75gfr6g4q3xgqdm325-python3-3.6.6/lib -lpython3.6m -Xlinker -export-dynamic -lpthread -ldl -lcrypt -lncurses -lutil -lm >&5
/nix/store/h0lbngpv6ln56hjj59i6l77vxq25flbz-binutils-2.30/bin/ld: cannot find -lncurses
collect2: error: ld returned 1 exit status
configure:20032: $? = 1