Increase logging around bad dex files.

Change-Id: I294aecd401046537004c79dcd0041b61af962892
diff --git a/src/dex_file.cc b/src/dex_file.cc
index 11ddcd5..0f0bed4 100644
--- a/src/dex_file.cc
+++ b/src/dex_file.cc
@@ -71,6 +71,7 @@
     }
     UniquePtr<ZipEntry> zip_entry(zip_archive->Find(kClassesDex));
     if (zip_entry.get() == NULL) {
+      LOG(ERROR) << "Zip archive '" << filename << "' doesn't contain " << kClassesDex;
       return false;
     }
     checksum = zip_entry->GetCrc32();
@@ -84,6 +85,7 @@
     checksum = dex_file->GetHeader().checksum_;
     return true;
   }
+  LOG(ERROR) << "Expected valid zip or dex file name: " << filename;
   return false;
 }
 
diff --git a/src/utils.cc b/src/utils.cc
index 1456495..94d812c 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -1204,7 +1204,9 @@
 
 std::string GetArtCacheFilenameOrDie(const std::string& location) {
   std::string art_cache(GetArtCacheOrDie(GetAndroidData()));
-  CHECK_EQ(location[0], '/') << location;
+  if (location[0] != '/') {
+    LOG(FATAL) << "Expected path in location to be absolute: "<< location;
+  }
   std::string cache_file(location, 1); // skip leading slash
   std::replace(cache_file.begin(), cache_file.end(), '/', '@');
   return art_cache + "/" + cache_file;