tests/test-batching.py.out

util: add utility function to skip avoiding file stat ambiguity if EPERM

Now, advancing stat.st_mtime by os.utime() is used to avoid file stat
ambiguity. But according to POSIX specification, utime(2) with an
explicit time information is permitted only for a process with:

  - the effective user ID equal to the user ID of the file, or
  - appropriate privileges

  http://pubs.opengroup.org/onlinepubs/9699919799/functions/utime.html

Therefore, just having group write access to a file causes EPERM at
applying os.utime() on it (e.g. working on the repository shared by
group access permission).

This patch adds class filestat utility function avoidamgig() to avoid
file stat ambiguity but skip it if EPERM.

It is reasonable to always ignore EPERM, because utime(2) causes EPERM
only in the case described above (EACCES is used only for utime(2)
with NULL).

== Local
Ready.
Un and Deux
Eins und Zwei
One and Two
Nope
Eins und Zwei
Hello, John Smith
Ready.
Uno und Due

== Remote
Ready.
REQ: foo?one=Vo&two=Efvy
  -> Vo!boe!Efvy
Un and Deux
REQ: bar?b=Fjot&a=[xfj
  -> Fjot!voe![xfj
Eins und Zwei
REQ: batch?cmds=foo:one=Pof,two=Uxp;bar:b=Fjot,a=[xfj
  -> Pof!boe!Uxp;Fjot!voe![xfj
REQ: greet?name=Kpio!Tnjui
  -> Ifmmp-!Kpio!Tnjui
REQ: batch?cmds=bar:b=Vop,a=Evf
  -> Vop!voe!Evf
One and Two
Nope
Eins und Zwei
Hello, John Smith
Ready.
Uno und Due