flutter analyze: handle missing files

packages/flutter_tools/lib/src/commands/analyze.dart

@@ -361,6 +361,7 @@ linter:
     RegExp constructorTearOffsPattern = new RegExp('.+#.+// analyzer doesn\'t like constructor tear-offs');
     RegExp ignorePattern = new RegExp(r'// analyzer says "([^"]+)"');
     RegExp conflictingNamesPattern = new RegExp('^The imported libraries \'([^\']+)\' and \'([^\']+)\' cannot have the same name \'([^\']+)\'\$');
+    RegExp missingFilePattern = new RegExp('^Target of URI does not exist: \'([^\')]+)\'\$');
 
     Set<String> changedFiles = new Set<String>(); // files about which we've complained that they changed
 
@@ -393,8 +394,11 @@ linter:
           bool shouldIgnore = false;
           if (filename == mainFile.path) {
             Match libs = conflictingNamesPattern.firstMatch(errorMessage);
+            Match missing = missingFilePattern.firstMatch(errorMessage);
             if (libs != null) {
               errorLine = '[$level] $errorMessage (${dartFiles[lineNumber-1]})'; // strip the reference to the generated main.dart
+            } else if (missing != null) {
+              errorLine = '[$level] File does not exist (${missing[1]})';
             } else {
               errorLine += ' (Please file a bug on the "flutter analyze" command saying that you saw this message.)';
             }