cros_extract_deps -j writes JSON, sorted by package name.

Rationale: Consumers of this output should not have to eval() python
code in order to use the output. Also potentially useful for dumping
out of buildbot for consumption by other web-based tools.

Review URL: http://codereview.chromium.org/3148022

cros_extract_deps

@@ -5,8 +5,8 @@
 
 """Extract dependency tree out of emerge and make it accessible and useful."""
 
+import json
 import optparse
-import pprint
 import re
 import shutil
 import subprocess
@@ -23,6 +23,14 @@ class ParseException(Exception):
     return self.reason
 
 
+class SetEncoder(json.JSONEncoder):
+  """Custom json encoder class, doesn't hate set types."""
+  def default(self, o):
+    if isinstance(o, set):
+      return list(o)
+    return json.JSONEncoder.default(self, o)
+
+
 def GetDepLinesFromPortage(options, packages):
   """Get dependency lines out of emerge.
 
@@ -179,7 +187,7 @@ def main():
 
   lines = GetDepLinesFromPortage(options, packages)
   deps_map = ParseDepLines(lines)
-  output = pprint.pformat(deps_map)
+  output = json.dumps(deps_map, sort_keys=True, indent=2, cls=SetEncoder)
   if options.output:
     output_file = open(options.output, 'w')
     output_file.write(output)