title: Errors Upgrading SBT
body: <p>I am attempting to upgrade my Scala Play Framework application to 2.8, and this involves upgrading SBT to 1.x. </p>
  
  <p>In my <strong>build.propeties</strong> I have <code>sbt.version=1.3.5</code></p>
  
  <p>In <strong>plugins.sbt</strong> I have </p>
  
  <pre><code>addSbtPlugin("com.typesafe.play" % "sbt-plugin" % "2.7.4")
  </code></pre>
  
  <p>However, I see the following:</p>
  
  <pre><code>[warn] insecure HTTP request is deprecated 'http://repo.typesafe.com/typesafe/releases'; switch to HTTPS or opt-in as ("typesafe-releases" at "http://repo.typesafe.com/typesafe/releases").withAllowInsecureProtocol(true)
  [warn] insecure HTTP request is deprecated 'http://repo.typesafe.com/typesafe/releases'; switch to HTTPS or opt-in as ("typesafe-releases" at "http://repo.typesafe.com/typesafe/releases").withAllowInsecureProtocol(true)
  [warn] insecure HTTP request is deprecated 'http://repo.typesafe.com/typesafe/releases'; switch to HTTPS or opt-in as ("typesafe-releases" at "http://repo.typesafe.com/typesafe/releases").withAllowInsecureProtocol(true)
  [warn]  Note: Some unresolved dependencies have extra attributes.  Check that these dependencies exist with the requested attributes.
  [warn]      com.typesafe.play:sbt-plugin:2.7.4 (sbtVersion=1.0, scalaVersion=2.12)
  [error] sbt.librarymanagement.ResolveException: Error downloading com.typesafe.play:sbt-plugin;sbtVersion=1.0;scalaVersion=2.12:2.7.4
  [error]   Not found
  [error]   Not found
  [error]   not found: https://repo1.maven.org/maven2/com/typesafe/play/sbt-plugin_2.12_1.0/2.7.4/sbt-plugin-2.7.4.pom
  [error]   not found: /Users/Neil/.ivy2/local/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  [error]   not found: /Users/Neil/.activator/repository/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  [error]   not found: /usr/local/activator-1.3.6/repository/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  [error]   not found: http://dl.bintray.com/heroku/sbt-plugins/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  [error]   not found: http://dl.bintray.com/neomaclin/maven/com/typesafe/play/sbt-plugin_2.12_1.0/2.7.4/sbt-plugin-2.7.4.pom
  [error]   download error: Caught javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target (sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target) while downloading https://repo.scala-sbt.org/scalasbt/sbt-plugin-releases/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  [error]   download error: Caught javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target (sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target) while downloading https://repo.typesafe.com/typesafe/ivy-releases/com.typesafe.play/sbt-plugin/scala_2.12/sbt_1.0/2.7.4/ivys/ivy.xml
  </code></pre>
  
  <p>Here are my resolvers:</p>
  
  <pre><code>resolvers += Resolver.typesafeRepo("releases")
  resolvers += Resolver.typesafeIvyRepo("releases")
  resolvers += Resolver.sbtPluginRepo("releases")
  resolvers += Resolver.url("heroku-sbt-plugin-releases", url("http://dl.bintray.com/heroku/sbt-plugins/"))(Resolver.ivyStylePatterns)
  resolvers += Resolver.bintrayRepo("neomaclin", "maven")
  </code></pre>
  
  <p>What's causing all these warnings about using https? More importantly, when I look up those <code>ivy.xml</code> files, I get 404s but obviously those PKIX errors in the console. Why am I getting those when I am not behind a proxy? I guess I am using the wrong coordinates, but I can't figure out how they are wrong.</p>