src/bin/sage: Use python3 etc. from PATH instead of using SAGE_LOCAL

src/bin/sage

@@ -250,7 +250,7 @@ sage_setup() {
 # if Python and sage-location haven't been installed yet.
 maybe_sage_location()
 {
-    if [ -w "$SAGE_LOCAL" ]; then
+    if [ -n "$SAGE_LOCAL" -a -w "$SAGE_LOCAL" ]; then
         if [ -x "$SAGE_LOCAL/bin/python" ] && [ -x "$SAGE_LOCAL/bin/sage-location" ]; then
             sage-location || exit $?
         fi
@@ -520,39 +520,24 @@ fi
 # Run Sage's versions of Python, pip, IPython, Jupyter.
 #####################################################################
 
-if [ "$1" = '-pip' -o "$1" = '--pip' ]; then
+if [ "$1" = '-pip' -o "$1" = '--pip' -o "$1" = "--pip3" ]; then
     shift
-    exec sage-python -m pip "$@"
+    exec python3 -m pip "$@"
 fi
 
-if [ "$1" = '--pip3' ]; then
+if [ "$1" = '-python' -o "$1" = '--python' -o  "$1" = '-python3' -o "$1" = '--python3' ]; then
     shift
-    exec "$SAGE_LOCAL"/bin/python3 -m pip "$@"
+    exec python3 "$@"
 fi
 
-if [ "$1" = '-python' -o "$1" = '--python' ]; then
+if [ "$1" = '-ipython' -o "$1" = '--ipython' -o "$1" = '-ipython3' -o "$1" = '--ipython3' ]; then
     shift
-    exec "$SAGE_LOCAL"/bin/python3 "$@"
-fi
-
-if [ "$1" = '-python3' -o "$1" = '--python3' ]; then
-    shift
-    exec "$SAGE_LOCAL"/bin/python3 "$@"
-fi
-
-if [ "$1" = '-ipython' -o "$1" = '--ipython' ]; then
-    shift
-    exec "$SAGE_LOCAL"/bin/ipython "$@"
-fi
-
-if [ "$1" = '-ipython3' -o "$1" = '--ipython3' ]; then
-    shift
-    exec "$SAGE_LOCAL"/bin/ipython3 "$@"
+    exec ipython3 "$@"
 fi
 
 if [ "$1" = '-jupyter' -o "$1" = '--jupyter' ]; then
     shift
-    exec "$SAGE_LOCAL"/bin/jupyter "$@"
+    exec jupyter "$@"
 fi
 
 #####################################################################
@@ -976,7 +961,7 @@ install() {
     done
     # Display a message if we actually installed something (using this
     # file, generated by sage-spkg, is a bit of a hack though)
-    if [ -f "$SAGE_LOCAL/lib/sage-force-relocate.txt" ]; then
+    if [ -n "$SAGE_LOCAL" -a -f "$SAGE_LOCAL/lib/sage-force-relocate.txt" ]; then
         echo
         echo "Warning: it might be needed to update the Sage library before"
         echo "installed packages work: you should run 'make' from \$SAGE_ROOT"