add next NEST release candidate 3.4-rc2

packages/nest/package.py

@@ -27,7 +27,7 @@ class Nest(CMakePackage):
     git      = "https://github.com/nest/nest-simulator.git"
 
     version('master', branch='master')
-    version('3.4_rc1',sha256='62558bf545abd5a54e92abd4ce8afaa58b45fe1065e6f47a7da723cd85a7e013')
+    version('3.4_rc2',sha256='037012200489ad4f800ed5dc6279917e89c831d101a4b852b5c42278923566a3')
     version('3.3',    sha256='179462b966cc61f5785d2fee770bc36f86745598ace9cd97dd620622b62043ed')
     version('3.2',    sha256='583d5725882ad5e8fd4fc7ffab425da97cbbb91fadbc327e940c184e8892b958')
     patch('nest-simulator-3.2-p1-VersionNumber.patch', when='@3.2')