plugins/pyenv: use `_command_exists`

clean_files.txt

@@ -90,6 +90,7 @@ plugins/available/history.plugin.bash
 plugins/available/hub.plugin.bash
 plugins/available/jump.plugin.bash
 plugins/available/node.plugin.bash
+plugins/available/pyenv.plugin.bash
 plugins/available/rbenv.plugin.bash
 plugins/available/textmate.plugin.bash
 plugins/available/xterm.plugin.bash

plugins/available/pyenv.plugin.bash

@@ -1,10 +1,13 @@
+# shellcheck shell=bash
 cite about-plugin
 about-plugin 'load pyenv, if you are using it'
 
 export PYENV_ROOT="$HOME/.pyenv"
 pathmunge "$PYENV_ROOT/bin"
 
-[[ `which pyenv 2>/dev/null` ]] && eval "$(pyenv init - bash)"
+if _command_exists pyenv; then
+	eval "$(pyenv init - bash)"
+fi
 
 #Load pyenv virtualenv if the virtualenv plugin is installed.
 if pyenv virtualenv-init - &> /dev/null; then