title: Invalid `Podfile` file: cannot load such file. /flutter/packages/flutter_tools/bin/podhelper
body: <p>When I tried to test flutter project with a simulator after upgrading flutter, this error came up.</p>
  <pre><code>Launching lib/main.dart on iPhone 11 Pro in debug mode...
  Running pod install...                                              1.1s
  CocoaPods' output:
  ↳
      [!] Invalid `Podfile` file: cannot load such file -- /Volumes/WD /DEVELOPER/flutter/packages/flutter_tools/bin/podhelper.
       #  from /Volumes/WD/DEVELOPER/dont_forget/ios/Podfile:26
       #  -------------------------------------------
       #
       &gt;  require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
       #
       #  -------------------------------------------
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:318:in `rescue in block in from_ruby'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:312:in `block in from_ruby'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:50:in `instance_eval'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:50:in `initialize'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:310:in `new'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:310:in `from_ruby'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.0.beta.2/lib/cocoapods-core/podfile.rb:276:in `from_file'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0.beta.2/lib/cocoapods/config.rb:205:in `podfile'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0.beta.2/lib/cocoapods/command.rb:160:in `verify_podfile_exists!'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0.beta.2/lib/cocoapods/command/install.rb:46:in `run'
      /Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:334:in `run'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0.beta.2/lib/cocoapods/command.rb:52:in `run'
      /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0.beta.2/bin/pod:55:in `&lt;top (required)&gt;'
      /usr/local/bin/pod:23:in `load'
      /usr/local/bin/pod:23:in `&lt;main&gt;'
  Error running pod install
  Error launching application on iPhone 11 Pro.
  Exited (sigterm)
  </code></pre>
  <p>I tried <code>flutter clean</code>, <code>flutter build iOS</code>, <code>rm iOS/Podfile</code> but it didn't work at all. How can I solve this? Here's my <code>flutter doctor</code> and <code>flutter --version</code> below.</p>
  <pre><code>Doctor summary (to see all details, run flutter doctor -v):
  [✓] Flutter (Channel stable, 1.20.2, on Mac OS X 10.15.5 19F101, locale en-KR)
   
  [✓] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
  [✓] Xcode - develop for iOS and macOS (Xcode 11.6)
  [✓] Android Studio (version 4.0)
  [✓] VS Code (version 1.48.1)
  [✓] Connected device (1 available)
  
  • No issues found!
  </code></pre>
  <pre><code>Flutter 1.20.2 • channel stable • https://github.com/flutter/flutter.git
  Framework • revision bbfbf1770c (10 days ago) • 2020-08-13 08:33:09 -0700
  Engine • revision 9d5b21729f
  Tools • Dart 2.9.1
  </code></pre>