Better error when requesting a show by ID which doesn't exist

Closes #54

tests/test_tvdb_api.py

@@ -101,6 +101,12 @@ def test_shownotfound(self):
         with pytest.raises(tvdb_shownotfound):
             self.t['the fake show thingy']
 
+    def test_shownotfound(self):
+        """Checks exception is thrown when episode doesn't exist.
+        """
+        with pytest.raises(tvdb_shownotfound):
+            self.t[999999999999999]
+
     def test_episodenotfound(self):
         """Checks exception is raised for non-existent episode
         """

tvdb_api.py

@@ -864,10 +864,16 @@ def _loadUrl(self, url, data=None, recache=False, language=None):
                 # raise(tvdb_resourcenotfound)
                 # handle no data at a different level so it is more specific
                 pass
-            if error == u'Not Authorized':
+            elif error == u'Not Authorized':
                 raise(tvdb_notauthorized)
+            elif error.startswith(u"ID: ") and error.endswith("not found"):
+                # FIXME: Refactor error out of in this method
+                raise tvdb_shownotfound("%s" % error)
+            else:
+                raise tvdb_error("%s" % error)
+
         if errors:
-            if u'invalidLanguage' in errors:
+            if errors and u'invalidLanguage' in errors:
                 # raise(tvdb_invalidlanguage(errors[u'invalidLanguage']))
                 # invalidLanguage does not mean there is no data
                 # there is just less data