execute subcommands in parent enviornment (resepect http_proxy and

similar)

sau/helpers.py

@@ -1,17 +1,21 @@
 import logging
+import os
 import subprocess
 import time
 
 import sau
 
 def exec_cmd(cmd, timeout=900, env = None):
+    my_env = os.environ.copy()
+    if env:
+        my_env.update(env)
     log = logging.getLogger(sau.LOGNAME)
     log.debug('Executing "{}"'.format(' '.join(cmd)))
     proc = subprocess.Popen(
             cmd,
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
-            env = env)
+            env = my_env)
     out = b""
     err = b""