Added logging of additional debugging information to nsenter function

Previosuly we haven't logged the output of the STDERR, only the STDOUT.
Additionally we haven't logged the return code.
This patch fixes that.

Signed-off-by: Lev Veyde <lveyde@redhat.com>

src/imgbased/command.py

@@ -18,7 +18,6 @@ def call(*args, **kwargs):
 
 
 def nsenter(arg, new_root=None, shell=False, environ=None):
-    DEVNULL = open(os.devnull, "w")
     if new_root:
         if shell:
             arg = "nsenter --root={0} --wd={0} {1}".format(new_root, arg)
@@ -31,10 +30,12 @@ def nsenter(arg, new_root=None, shell=False, environ=None):
     environ = environ or os.environ
     log.debug("Executing: %s", arg)
     proc = subprocess.Popen(arg, stdout=subprocess.PIPE, env=environ,
-                            stderr=DEVNULL, shell=shell).communicate()
-    ret = proc[0]
-    log.debug("Result: %s", repr(ret))
-    return ret
+                            stderr=subprocess.PIPE, shell=shell)
+    stdout, stderr = proc.communicate()
+    log.debug("STDOUT: %s", repr(stdout))
+    log.debug("STDERR: %s", repr(stderr))
+    log.debug("ReturnCode: %s", repr(proc.returncode))
+    return stdout
 
 
 def chroot(args, root):