title: Upgraded to sbt 0.13.9; now I cannot launch sbt
body: <p>I upgraded sbt from version 0.13.8 to 0.13.9. We have Nexus proxying many repositories. Now, when I issue 'sbt' command - I get unresolved dependencies</p>
  
  <pre><code>scala-library
  scala-compilre
  scala-reflect 
  </code></pre>
  
  <p>all due to sha1 different from the computed. Is there a way to bypass sha1 validation?
  FYI. setting <code>checksums in update := Nil</code> in <code>build.sbt</code> does not solve the problem. I even tried putting
  <code>&lt;property name="ivy.checksums" value=""/&gt;</code> in <code>~/.ivy/ivysettings.xml</code> still fails.</p>
  
  <p>here is the console output:</p>
  
  <pre><code>D:\Temp\test&gt;sbt -v update
  Getting org.scala-sbt sbt 0.13.9 ...
  
  :: problems summary ::
  :::: WARNINGS
          problem while downloading module descriptor: http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.pom: invalid sha1: expected=c39e31e37ce77d8d5fb8e8c640222275815d36f2 computed=4e8b721680f2defb491fe90447302658d464d5c
  0 (351ms)
  
                  module not found: org.scala-lang#scala-library;2.10.5
  
          ==== local: tried
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-library\2.10.5\ivys\ivy.xml
  
            -- artifact org.scala-lang#scala-library;2.10.5!scala-library.jar:
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-library\2.10.5\jars\scala-library.jar
  
          ==== my-ivy-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/ivy-releases/org.scala-lang/scala-library/2.10.5/ivys/ivy.xml
  
          ==== my-maven-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.pom
  
          problem while downloading module descriptor: http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.pom: invalid sha1: expected=9a85822af1f9ea46b49dfdfa99eafc0bd819abaf computed=c3e0b6cf2f45a5a7cb052ef9e00f8fdac55e7
  1b7 (69ms)
  
                  module not found: org.scala-lang#scala-compiler;2.10.5
  
          ==== local: tried
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-compiler\2.10.5\ivys\ivy.xml
  
            -- artifact org.scala-lang#scala-compiler;2.10.5!scala-compiler.jar:
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-compiler\2.10.5\jars\scala-compiler.jar
  
          ==== my-ivy-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/ivy-releases/org.scala-lang/scala-compiler/2.10.5/ivys/ivy.xml
  
          ==== my-maven-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.pom
  
          problem while downloading module descriptor: http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.pom: invalid sha1: expected=3a6fa11041ac0c8b4d5fcf9d4f1372ba8c0b7216 computed=30f1f646114a79eeefb254ead190f045c460564
  9 (67ms)
  
                  module not found: org.scala-lang#scala-reflect;2.10.5
  
          ==== local: tried
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-reflect\2.10.5\ivys\ivy.xml
  
            -- artifact org.scala-lang#scala-reflect;2.10.5!scala-reflect.jar:
  
            C:\Users\ak\.ivy2\local\org.scala-lang\scala-reflect\2.10.5\jars\scala-reflect.jar
  
          ==== my-ivy-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/ivy-releases/org.scala-lang/scala-reflect/2.10.5/ivys/ivy.xml
  
          ==== my-maven-proxy-releases: tried
  
            http://nexusserver:8081/nexus/content/groups/mvn-repositories/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.pom
  
                  ::::::::::::::::::::::::::::::::::::::::::::::
  
                  ::          UNRESOLVED DEPENDENCIES         ::
  
                  ::::::::::::::::::::::::::::::::::::::::::::::
  
                  :: org.scala-lang#scala-library;2.10.5: not found
  
                  :: org.scala-lang#scala-compiler;2.10.5: not found
  
                  :: org.scala-lang#scala-reflect;2.10.5: not found
  
                  ::::::::::::::::::::::::::::::::::::::::::::::
  
  
  
  :: USE VERBOSE OR DEBUG MESSAGE LEVEL FOR MORE DETAILS
  unresolved dependency: org.scala-lang#scala-library;2.10.5: not found
  unresolved dependency: org.scala-lang#scala-compiler;2.10.5: not found
  unresolved dependency: org.scala-lang#scala-reflect;2.10.5: not found
  Error during sbt execution: Error retrieving required libraries
    (see C:\Users\ak\.sbt\boot\update.log for complete log)
  Error: Could not retrieve sbt 0.13.9
  </code></pre>