Organize error checking in virtualenwrapper plugin

plugins/virtualenvwrapper/virtualenvwrapper.plugin.zsh

@@ -6,15 +6,22 @@ elif [[ -f "/etc/bash_completion.d/virtualenvwrapper" ]]; then
   virtualenvwrapper="/etc/bash_completion.d/virtualenvwrapper"
   source "/etc/bash_completion.d/virtualenvwrapper"
 else
-  print "zsh virtualenvwrapper plugin: Cannot find ${virtualenvwrapper}. Please install with \`pip install virtualenvwrapper\`."
+  print "zsh virtualenvwrapper plugin: Cannot find ${virtualenvwrapper}.\n"\
+        "Please install with \`pip install virtualenvwrapper\`" >&2
+  return
+fi
+if ! type workon &>/dev/null; then
+  print "zsh virtualenvwrapper plugin: shell function 'workon' not defined.\n"\
+        "Please check ${virtualenvwrapper}" >&2
   return
 fi
 
-if type workon 2>&1 >/dev/null; then
-  if [[ "$WORKON_HOME" == "" ]]; then
-    echo "\$WORKON_HOME is not defined so ZSH plugin virtualenvwrapper will not work"
-  else
-    if [[ ! $DISABLE_VENV_CD -eq 1 ]]; then
+if [[ "$WORKON_HOME" == "" ]]; then
+  print "\$WORKON_HOME is not defined so ZSH plugin virtualenvwrapper will not work" >&2
+  return
+fi
+
+if [[ ! $DISABLE_VENV_CD -eq 1 ]]; then
   # Automatically activate Git projects's virtual environments based on the
   # directory name of the project. Virtual environment name can be overridden
   # by placing a .venv file in the project root with a virtualenv name in it
@@ -65,8 +72,4 @@ if type workon 2>&1 >/dev/null; then
   else
     set -A chpwd_functions workon_cwd
   fi
-    fi
-  fi
-else
-  print "zsh virtualenvwrapper plugin: shell function 'workon' not defined. Please check ${virtualenvwrapper}." >&2
 fi