Fail with name of the file

Change-Id: I547c876a6974609e29b14a01b7bec34648551153
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/events/logging/log_backend.cc b/aos/events/logging/log_backend.cc
index 9eb9089..6cd9a7d 100644
--- a/aos/events/logging/log_backend.cc
+++ b/aos/events/logging/log_backend.cc
@@ -351,7 +351,8 @@
   std::vector<std::string> names;
   const std::string prefix = absl::StrCat(base_name_, separator_);
   for (const auto &file : files) {
-    CHECK(absl::StartsWith(file, prefix));
+    CHECK(absl::StartsWith(file, prefix))
+        << ": File " << file << ", prefix " << prefix;
     names.push_back(file.substr(prefix.size()));
   }
   return names;