Execute(ale#util#EscapePCRE should escape strings for PCRE or RE2 appropriately):
  AssertEqual '\\\^\$\*\+\?\.\(\)\|\{\}\[\]', ale#util#EscapePCRE('\^$*+?.()|{}[]')
  AssertEqual 'abcABC09', ale#util#EscapePCRE('abcABC09')
  AssertEqual '/', ale#util#EscapePCRE('/')
