Fixes #1860. Subversion builds sequentially due to race.

lib/spack/spack/graph.py

@@ -522,7 +522,7 @@ def graph_dot(specs, deptype=None, static=False, out=None):
 
     out.write('digraph G {\n')
     out.write('  labelloc = "b"\n')
-    out.write('  rankdir = "LR"\n')
+    out.write('  rankdir = "TB"\n')
     out.write('  ranksep = "5"\n')
     out.write('node[\n')
     out.write('     fontname=Monaco,\n')

var/spack/repos/builtin/packages/subversion/package.py

@@ -46,6 +46,9 @@ class Subversion(Package):
     # depends_on('perl')
     # depends_on('ruby')
 
+    # Installation has race cases.
+    parallel = False
+
     def install(self, spec, prefix):
 
         # configure, build, install: