Add ignore pretty.

Author: nikomatsakis

src/test/run-pass/associated-types-where-clause-impl-ambiguity.rs

@@ -14,6 +14,8 @@
 // for `ByRef`. The right answer was to consider the result ambiguous
 // until more type information was available.
 
+// ignore-pretty -- FIXME(#17362) pretty prints with `<<` which lexes wrong
+
 #![feature(associated_types, lang_items, unboxed_closures)]
 #![no_implicit_prelude]