[PATCH v3] pwclient: Fix silent crash on python 2

[Robin Jarry]

Replacing sys.stdout and sys.stderr can cause obscure crashes when
trying to write non unicode data. The interpreter is terminated with
SIGINT without any specific error writen on the console.

  rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x7f964820e8d0},
  {0x559f50, [], SA_RESTORER, 0x7f964820e8d0}, 8) = 0

This happens easily when there is an untrapped exception which should
lead to printing a traceback on stderr.

The only way to prevent UnicodeEncodeErrors is to make sure that one of
the locale-related environment variables (LC_ALL, LANG, LANGUAGE, etc.)
is set. Python will use the correct encoding accordingly.

Add a note about this on `pwclient --help`. Also, display a help message
when an encoding error occurs.

Fixes: 046419a3bf8f ("pwclient: Fix encoding problems")
Signed-off-by: Robin Jarry <robin.jarry at 6wind.com>
---

v3: Removed all hacks and added explicit error messages to avoid these encoding
errors completely.

Examples:

  $ cat ~/.pwclientrc
  [options]
  default = dpdk
  [dpdk]
  url= http://dpdk.org/dev/patchwork/xmlrpc/

  $ LANG= LC_ALL= PAGER= LANGUAGE= ./patchwork/bin/pwclient view 17892
  Traceback (most recent call last):
    File "./patchwork/bin/pwclient", line 823, in <module>
      main()
    File "./patchwork/bin/pwclient", line 768, in main
      print(s)
  UnicodeEncodeError: 'ascii' codec can't encode character u'\u0142' in position
  468: ordinal not in range(128)

  Try exporting the LANG or LC_ALL env vars. See pwclient --help for more details.

  $ ./patchwork/bin/pwclient --help
  usage: pwclient [-h]
                  {apply,git-am,get,info,projects,check-list,check-info,check-create,states,view,update,list,search}
                  ...

  Important: to avoid unicode encode/decode errors, you should export the LANG
  or LC_ALL environment variables according to the configured locales on your
  system. If these variables are already set, make sure that they point on valid
  and installed locales.
  [...]

 patchwork/bin/pwclient | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/patchwork/bin/pwclient b/patchwork/bin/pwclient
index ed0351bf5288..037099dbc8ba 100755
--- a/patchwork/bin/pwclient
+++ b/patchwork/bin/pwclient
@@ -41,16 +41,7 @@ except ImportError:
 import shutil
 import re
 import io
-import locale
 
-if sys.version_info.major == 2:
-    # hack to make writing unicode to standard output/error work on Python 2
-    OUT_ENCODING = (sys.stdout.encoding or locale.getpreferredencoding() or
-                    os.getenv('PYTHONIOENCODING', 'utf-8'))
-    sys.stdout = io.open(sys.stdout.fileno(), mode='w',
-                         encoding=OUT_ENCODING, errors='replace')
-    sys.stderr = io.open(sys.stderr.fileno(), mode='w',
-                         encoding=OUT_ENCODING, errors='replace')
 
 # Default Patchwork remote XML-RPC server URL
 # This script will check the PW_XMLRPC_URL environment variable
@@ -461,6 +452,12 @@ def main():
 
     action_parser = argparse.ArgumentParser(
         prog='pwclient',
+        description='''
+        Important: to avoid unicode encode/decode errors, you should export the
+        LANG or LC_ALL environment variables according to the configured locales
+        on your system. If these variables are already set, make sure that they
+        point on valid and installed locales.
+        ''',
         epilog='Use \'pwclient <command> --help\' for more info',
     )
 
@@ -822,4 +819,12 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except (UnicodeEncodeError, UnicodeDecodeError) as e:
+        import traceback
+        traceback.print_exc()
+        sys.stderr.write('''
+Try exporting the LANG or LC_ALL env vars. See pwclient --help for more details.
+''')
+        sys.exit(1)
-- 
2.11.0.193.g1d1bdafd6426