Use consistent selector error

src/command-registry.coffee

@@ -2,7 +2,7 @@
 {specificity} = require 'clear-cut'
 _ = require 'underscore-plus'
 {$} = require './space-pen-extensions'
-{isSelectorValid} = require './selector-parser'
+{validateSelector} = require './selector-parser'
 
 SequenceCount = 0
 SpecificityCache = {}
@@ -88,8 +88,7 @@ class CommandRegistry
       return disposable
 
     if typeof target is 'string'
-      unless isSelectorValid(target)
-        throw new Error("'#{target}' is not a valid selector")
+      validateSelector(target)
       @addSelectorBasedListener(target, commandName, callback)
     else
       @addInlineListener(target, commandName, callback)

src/context-menu-manager.coffee

@@ -8,7 +8,7 @@ fs = require 'fs-plus'
 {Disposable} = require 'event-kit'
 Grim = require 'grim'
 MenuHelpers = require './menu-helpers'
-{isSelectorValid} = require './selector-parser'
+{validateSelector} = require './selector-parser'
 
 SpecificityCache = {}
 
@@ -124,8 +124,7 @@ class ContextMenuManager
     addedItemSets = []
 
     for selector, items of itemsBySelector
-      unless isSelectorValid(selector)
-        throw new Error("'#{selector}' is not a valid selector")
+      validateSelector(selector)
 
       itemSet = new ContextMenuItemSet(selector, items)
       addedItemSets.push(itemSet)

src/selector-parser.coffee

@@ -1,6 +1,13 @@
 selectorCache = null
 testElement = null
 
+exports.validateSelector = (selector) ->
+  return if exports.isSelectorValid(selector)
+
+  error = new Error("'#{selector}' is not a valid selector")
+  error.code = 'EBADSELECTOR'
+  throw error
+
 exports.isSelectorValid = (selector) ->
   selectorCache ?= {}
   cachedValue = selectorCache[selector]