parallel_emerge: Fix builds when PORTAGE_BINHOST is unset

parallel_emerge

Index: parallel_emerge
diff --git a/parallel_emerge b/parallel_emerge
index 49cf7b2f4d1e29caafc786bcf301ecab9c14b239..12548fa878444c88c91de6667fd710dce7622f00 100755
--- a/parallel_emerge
+++ b/parallel_emerge
@@ -744,17 +744,24 @@ class DepGraphGenerator(object):
       if this_pkg["action"] == "nomerge":
         this_pkg["action"] = "merge"
 
-    def RemotePackageDatabase():
+    def RemotePackageDatabase(binhost_url):
       """Grab the latest binary package database from the prebuilt server.
 
       We need to know the modification times of the prebuilt packages so that we
       know when it is OK to use these packages and when we should rebuild them
       instead.
 
+      Args:
+        binhost_url: Base URL of remote packages (PORTAGE_BINHOST).
+
       Returns:
         A dict mapping package identifiers to modification times.
       """
-      url = self.emerge.settings["PORTAGE_BINHOST"] + "/Packages"
+
+      if not binhost_url:
+        return {}
+
+      url = binhost_url + "/Packages"
 
       prebuilt_pkgs = {}
       f = urllib2.urlopen(url)
@@ -953,7 +960,7 @@ class DepGraphGenerator(object):
       cycles = FindCycles()
       if self.rebuild:
         local_pkgs = LocalPackageDatabase()
-        remote_pkgs = RemotePackageDatabase()
+        remote_pkgs = RemotePackageDatabase(emerge.settings["PORTAGE_BINHOST"])
         AutoRebuildDeps(local_pkgs, remote_pkgs, cycles)
 
     # We need to remove installed packages so that we can use the dependency