Catch any FileSystemException thrown when trying to read the template manifest during flutter create (#145620)

Fixes flutter/flutter#145423

Author: andrewkolos

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

@@ -669,8 +669,18 @@ abstract class CreateBase extends FlutterCommand {
       'templates',
       'template_manifest.json',
     );
+    final String manifestFileContents;
+    try {
+      manifestFileContents = globals.fs.file(manifestPath).readAsStringSync();
+    } on FileSystemException catch (e) {
+      throwToolExit(
+        'Unable to read the template manifest at path "$manifestPath".\n'
+        'Make sure that your user account has sufficient permissions to read this file.\n'
+        'Exception details: $e',
+      );
+    }
     final Map<String, Object?> manifest = json.decode(
-      globals.fs.file(manifestPath).readAsStringSync(),
+      manifestFileContents,
     ) as Map<String, Object?>;
     return Set<Uri>.from(
       (manifest['files']! as List<Object?>).cast<String>().map<Uri>(

packages/flutter_tools/test/commands.shard/permeable/create_test.dart

@@ -7,6 +7,7 @@ import 'dart:convert';
 import 'dart:io' as io;
 
 import 'package:args/command_runner.dart';
+import 'package:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/android/gradle_utils.dart' show templateAndroidGradlePluginVersion, templateAndroidGradlePluginVersionForModule, templateDefaultGradleVersion;
@@ -3749,6 +3750,40 @@ void main() {
 
     expect(rawManifestJson.contains(expectedDescription), isTrue);
   });
+
+  testUsingContext('flutter create should tool exit if the template manifest cannot be read', () async {
+    globals.fs.file(globals.fs.path.join(
+      Cache.flutterRoot!,
+      'packages',
+      'flutter_tools',
+      'templates',
+      'template_manifest.json',
+    )).createSync(recursive: true);
+
+    final CreateCommand command = CreateCommand();
+    final CommandRunner<void> runner = createTestCommandRunner(command);
+
+    await expectLater(
+      runner.run(<String>[
+        'create',
+        '--no-pub',
+        '--template=plugin',
+        '--project-name=test',
+        projectDir.path,
+      ]),
+      throwsToolExit(message: 'Unable to read the template manifest at path'),
+    );
+  }, overrides: <Type, Generator>{
+    FileSystem: () => MemoryFileSystem.test(
+      opHandle: (String context, FileSystemOp operation) {
+        if (operation == FileSystemOp.read && context.contains('template_manifest.json')) {
+          throw io.PathNotFoundException(
+              context, const OSError(), 'Cannot open file');
+        }
+      },
+    ),
+    ProcessManager: () => fakeProcessManager,
+  });
 }
 
 Future<void> _createProject(