bitbake/data/runqueue: Sync up with upstream to clean up environment variable handling

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data.py

@@ -234,25 +234,20 @@ def emit_env(o=sys.__stdout__, d = init(), all=False):
         for key in keys:
             emit_var(key, o, d, all and not isfunc) and o.write('\n')
 
-def export_vars(d):
-    keys = (key for key in d.keys() if d.getVarFlag(key, "export"))
-    ret = {}
-    for k in keys:
-        try:
-            v = d.getVar(k, True)
-            if v: 
-                ret[k] = v
-        except (KeyboardInterrupt, bb.build.FuncFailed):
-            raise
-        except Exception, exc:
-            pass
-    return ret
+def exported_keys(d):
+    return (key for key in d.keys() if not key.startswith('__') and
+                                      d.getVarFlag(key, 'export') and
+                                      not d.getVarFlag(key, 'unexport'))
 
-def export_envvars(v, d):
-    for s in os.environ.keys():
-        if s not in v:
-            v[s] = os.environ[s]
-    return v
+def exported_vars(d):
+    for key in exported_keys(d):
+        try:
+            value = d.getVar(key, True)
+        except Exception:
+            pass
+
+        if value is not None:
+            yield key, str(value)
 
 def emit_func(func, o=sys.__stdout__, d = init()):
     """Emits all items in the data store in a format such that it can be sourced by a shell."""