make patch_n2v guess paths

patch_n2v.sh

@@ -1,5 +1,15 @@
 #!/bin/bash
 
+set -e
+
+if [[ -z "$CONDA_PREFIX" ]]; then
+	echo "You do not seem to have an active conda environment active, aborting"
+	exit 1
+fi
+PYTHON_VERSION=$(python --version | sed -e 's/.* \([0-9]\.[0-9]\{2\}\).*/\1/')
+echo "Detected python v$PYTHON_VERSION"
+N2V_DIR="$CONDA_PREFIX/lib/python$PYTHON_VERSION/site-packages/n2v"
+
 case $1 in
 r | reset)
 	echo "Unpatching n2v"
@@ -7,12 +17,21 @@ r | reset)
 	cp -v n2v.bak/inverter.py n2v/inverter.py
 	cp -v n2v.bak/methods/zmp.py n2v/methods/zmp.py
 	cp -v n2v.bak/grid/grider.py n2v/grid/grider.py
+	echo "Success"
 	;;
 *)
 	echo "Patching n2v"
+	if [[ ! -d n2v.bak ]]; then
+		echo "Backing up n2v ..."
+		cp -v -r $N2V_DIR n2v.bak
+		echo "Done"
+		echo
+	fi
+
 	cp -v n2v.patched/engines/psi4.py n2v/engines/psi4.py
 	cp -v n2v.patched/inverter.py n2v/inverter.py
 	cp -v n2v.patched/methods/zmp.py n2v/methods/zmp.py
 	cp -v n2v.patched/grid/grider.py n2v/grid/grider.py
+	echo "Success"
 	;;
 esac