title: stack new command failing to download build plan for lts-14.1
body: <p>Stack fails with a 404 HTTP status to download a build plan for lts-14.1:</p>
  
  <pre><code>$ stack new my-project
  
  [...]
  
  Downloading lts-14.1 build plan ...
  RedownloadInvalidResponse Request {
    host                 = "raw.githubusercontent.com"
    port                 = 443
    secure               = True
    requestHeaders       = []
    path                 = "/fpco/lts-haskell/master//lts-14.1.yaml"
    queryString          = ""
    method               = "GET"
    proxy                = Nothing
    rawBody              = False
    redirectCount        = 10
    responseTimeout      = ResponseTimeoutDefault
    requestVersion       = HTTP/1.1
  }
   "/home/michid/.stack/build-plan/lts-14.1.yaml" (Response {responseStatus = Status {statusCode = 404, statusMessage = "Not Found"}, responseVersion = HTTP/1.1, responseHeaders = [("Content-Security-Policy","default-src 'none'; style-src 'unsafe-inline'; sandbox"),("Strict-Transport-Security","max-age=31536000"),("X-Content-Type-Options","nosniff"),("X-Frame-Options","deny"),("X-XSS-Protection","1; mode=block"),("X-GitHub-Request-Id","10DA:4457:1D507:285B9:5D55DA2D"),("Content-Length","15"),("Accept-Ranges","bytes"),("Date","Thu, 15 Aug 2019 22:18:21 GMT"),("Via","1.1 varnish"),("Connection","keep-alive"),("X-Served-By","cache-mxp19828-MXP"),("X-Cache","MISS"),("X-Cache-Hits","0"),("X-Timer","S1565907502.529821,VS0,VE176"),("Vary","Authorization,Accept-Encoding"),("Access-Control-Allow-Origin","*"),("X-Fastly-Request-ID","9f869169dd207bbd8bb8a8fd4b274acf6580ba4f"),("Expires","Thu, 15 Aug 2019 22:23:21 GMT"),("Source-Age","0")], responseBody = (), responseCookieJar = CJ {expose = []}, responseClose' = ResponseClose})
  </code></pre>
  
  <p>Everything works fine if I specify <code>--resolver lts-13.19</code> on the command line so I'm assuming this is a bug.</p>
  
  <ul>
  <li>Anything I can do locally to work around this problem?</li>
  <li>What is the best place to report the issue or check whether it is a known one? I came across <a href="https://github.com/commercialhaskell/stack" rel="noreferrer">https://github.com/commercialhaskell/stack</a> but am not sure whether this is the right place. </li>
  </ul>