build/bin/sage-guess-package-system: Suppress error output

build/bin/sage-guess-package-system

@@ -1,21 +1,21 @@
 #!/usr/bin/env bash
 #
 # First test for user-installable package systems, then system package systems
-if conda --version > /dev/null; then
+if conda --version > /dev/null 2>&1; then
     echo conda
-elif brew --version > /dev/null; then
+elif brew --version > /dev/null 2>&1; then
     echo homebrew
-elif emerge --version > /dev/null; then
+elif emerge --version > /dev/null 2>&1; then
     echo gentoo
-elif apt-get --version > /dev/null; then
+elif apt-get --version > /dev/null 2>&1; then
     echo debian
-elif yum --version > /dev/null; then
+elif yum --version > /dev/null 2>&1; then
     echo fedora
-elif pacman --version > /dev/null; then
+elif pacman --version > /dev/null 2>&1; then
     echo arch
-elif zypper --version > /dev/null; then
+elif zypper --version > /dev/null 2>&1; then
     echo opensuse
-elif apk --version > /dev/null; then
+elif apk --version > /dev/null 2>&1; then
     echo alpine
 else
     case `uname -s` in