Added firstOrFail to belongsToMany.

src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php

@@ -5,6 +5,7 @@
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Query\Expression;
 use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Database\Eloquent\ModelNotFoundException;
 
 class BelongsToMany extends Relation {
 
@@ -87,6 +88,19 @@ public function first($columns = array('*'))
 		return count($results) > 0 ? $results->first() : null;
 	}
 
+	/**
+	 * Execute the query and get the first result or throw an exception.
+	 *
+	 * @param  array  $columns
+	 * @return \Illuminate\Database\Eloquent\Model|static
+	 */
+	public function firstOrFail($columns = array('*'))
+	{
+		if ( ! is_null($model = $this->first($columns))) return $model;
+
+		throw new ModelNotFoundException;
+	}
+
 	/**
 	 * Execute the query as a "select" statement.
 	 *
@@ -742,7 +756,7 @@ public function detach($ids = array(), $touch = true)
 	 * @return void
 	 */
 	public function touchIfTouching()
-	{ 
+	{
 	 	if ($this->touchingParent()) $this->getParent()->touch();
 
 	 	if ($this->getParent()->touches($this->relationName)) $this->touch();