title: npm rollbackFailedOptional error when install any package
body: <p>I have a problem when installing any <code>npm</code> packages. here is my error:</p>
  
  <p><code>rollbackFailedOptional: verb npm-session xxxxxxxxxxx</code></p>
  
  <p>for resolving this I do some stuff but I still get the same error. </p>
  
  <p>I put <code>registry=http://registry.npmjs.org/</code> in .<code>npmrc</code> file in my user folder and also run following commands:</p>
  
  <pre><code>npm config rm proxy
  npm config rm https-proxy
  </code></pre>
  
  <p>I try to solve the problem in node <code>8.11.1</code> and node <code>10.1.0</code> and my npm version is <code>5.6.0</code>.</p>
  
  <p>Why this problem occurs and how can resolve that?</p>
  
  <p><strong>Update:</strong>
  npm config list:</p>
  
  <pre><code>; cli configs
  metrics-registry = "http://registry.npmjs.org/"
  scope = ""
  user-agent = "npm/5.6.0 node/v8.11.1 win32 x64"
  
  ; userconfig C:\Users\me\.npmrc
  https-proxy = "https://username:password@proxy.company.com:6050/"
  proxy = "http://username:password@proxy.company.com:6050/"
  registry = "http://registry.npmjs.org/"
  
  ; builtin config undefined
  prefix = "C:\\Users\\me\\AppData\\Roaming\\npm"
  
  ; node bin location = C:\Program Files\nodejs\node.exe
  ; cwd = C:\Users\me
  ; HOME = C:\Users\me
  ; "npm config ls -l" to show all defaults.
  </code></pre>