The depend phase is safe to be always run as portage:portage if possible.

Index: trunk-droppriv-depend/pym/portage/__init__.py
===================================================================
--- trunk-droppriv-depend/pym/portage/__init__.py	(revision 7365)
+++ trunk-droppriv-depend/pym/portage/__init__.py	(working copy)
@@ -2326,7 +2326,7 @@
 
 # XXX This would be to replace getstatusoutput completely.
 # XXX Issue: cannot block execution. Deadlock condition.
-def spawn(mystring, mysettings, debug=0, free=0, droppriv=0, sesandbox=0, **keywords):
+def spawn(mystring, mysettings, debug=0, free=0, droppriv=0, forcedroppriv=0, sesandbox=0, **keywords):
 	"""
 	Spawn a subprocess with extra portage-specific options.
 	Optiosn include:
@@ -2352,6 +2352,8 @@
 	@type free: Boolean
 	@param droppriv: Drop to portage:portage when running this command
 	@type droppriv: Boolean
+	@param forcedroppriv: Forcibly drop to portage:portage when running this command
+	@type forcedroppriv: Boolean
 	@param sesandbox: Enable SELinux Sandboxing (toggles a context switch)
 	@type sesandbox: Boolean
 	@param keywords: Extra options encoded as a dict, to be passed to spawn
@@ -2444,7 +2446,7 @@
 
 	features = mysettings.features
 	restrict = mysettings.get("PORTAGE_RESTRICT","").split()
-	droppriv=(droppriv and "userpriv" in features and not \
+	droppriv=(forcedroppriv or droppriv and "userpriv" in features and not \
 		("nouserpriv" in restrict or "userpriv" in restrict))
 	if droppriv and not uid and portage_gid and portage_uid:
 		keywords.update({"uid":portage_uid,"gid":portage_gid,
@@ -3756,7 +3758,7 @@
 				pr, pw = os.pipe()
 				fd_pipes = {0:0, 1:1, 2:2, 9:pw}
 				mypids = spawn(EBUILD_SH_BINARY + " depend", mysettings,
-					fd_pipes=fd_pipes, returnpid=True)
+					fd_pipes=fd_pipes, returnpid=True, forcedroppriv=1)
 				os.close(pw) # belongs exclusively to the child process now
 				maxbytes = 1024
 				mybytes = []
@@ -3784,7 +3786,7 @@
 				mysettings["dbkey"] = \
 					os.path.join(mysettings.depcachedir, "aux_db_key_temp")
 
-			return spawn(EBUILD_SH_BINARY + " depend", mysettings)
+			return spawn(EBUILD_SH_BINARY + " depend", mysettings, forcedroppriv=1)
 
 		# Validate dependency metadata here to ensure that ebuilds with invalid
 		# data are never installed (even via the ebuild command).
@@ -4025,14 +4027,14 @@
 
 		# args are for the to spawn function
 		actionmap = {
-"depend": {"cmd":ebuild_sh, "args":{"droppriv":1, "free":0,         "sesandbox":0}},
-"setup":  {"cmd":ebuild_sh, "args":{"droppriv":0, "free":1,         "sesandbox":0}},
-"unpack": {"cmd":ebuild_sh, "args":{"droppriv":1, "free":0,         "sesandbox":sesandbox}},
-"compile":{"cmd":ebuild_sh, "args":{"droppriv":1, "free":nosandbox, "sesandbox":sesandbox}},
-"test":   {"cmd":ebuild_sh, "args":{"droppriv":1, "free":nosandbox, "sesandbox":sesandbox}},
-"install":{"cmd":ebuild_sh, "args":{"droppriv":0, "free":0,         "sesandbox":sesandbox}},
-"rpm":    {"cmd":misc_sh,   "args":{"droppriv":0, "free":0,         "sesandbox":0}},
-"package":{"cmd":misc_sh,   "args":{"droppriv":0, "free":0,         "sesandbox":0}},
+"depend": {"cmd":ebuild_sh, "args":{"droppriv":1, "forcedroppriv":1, "free":0,         "sesandbox":0}},
+"setup":  {"cmd":ebuild_sh, "args":{"droppriv":0, "forcedroppriv":0, "free":1,         "sesandbox":0}},
+"unpack": {"cmd":ebuild_sh, "args":{"droppriv":1, "forcedroppriv":0, "free":0,         "sesandbox":sesandbox}},
+"compile":{"cmd":ebuild_sh, "args":{"droppriv":1, "forcedroppriv":0, "free":nosandbox, "sesandbox":sesandbox}},
+"test":   {"cmd":ebuild_sh, "args":{"droppriv":1, "forcedroppriv":0, "free":nosandbox, "sesandbox":sesandbox}},
+"install":{"cmd":ebuild_sh, "args":{"droppriv":0, "forcedroppriv":0, "free":0,         "sesandbox":sesandbox}},
+"rpm":    {"cmd":misc_sh,   "args":{"droppriv":0, "forcedroppriv":0, "free":0,         "sesandbox":0}},
+"package":{"cmd":misc_sh,   "args":{"droppriv":0, "forcedroppriv":0, "free":0,         "sesandbox":0}},
 		}
 
 		# merge the deps in so we have again a 'full' actionmap