fix regression from commit 20bcbcc2

There were two places in the code that used the anti-pattern of
returning True on success else an error message. In python you should
always be able to replace `if x == True:` with just `if x:`. Which is
what the lint tool recommended. Unfortunately I didn't notice how the
return value was being used. This fixes that by changing the two
affected functions to return an error message or None on success.

This also adds `from __future__ import print_function` since the code
uses the `print(msg)` function form rather than the `print msg`
statement form. The former works by accident on python2 because the
parens are interpreted as creating parenthesized expression that
devolves to the single string inside the parens. So while the future
import isn't strictly speaking necessary it will help avoid mistakes in
the future if more complex `print()` calls are added.

Partial fix for #3620

share/tools/web_config/webconfig.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 
 from __future__ import unicode_literals
+from __future__ import print_function
 import binascii
 import cgi
 import glob
@@ -40,7 +41,6 @@ except ImportError:
 
 
 def run_fish_cmd(text):
-    from subprocess import PIPE
     # Ensure that fish is using UTF-8.
     ctype = os.environ.get("LC_ALL", os.environ.get("LC_CTYPE",
                                                     os.environ.get("LANG")))
@@ -51,12 +51,13 @@ def run_fish_cmd(text):
         # Fish makes the same assumption in config.fish
         env = os.environ.copy()
         env.update(LC_CTYPE="en_US.UTF-8", LANG="en_US.UTF-8")
-    p = subprocess.Popen([FISH_BIN_PATH], stdin=PIPE, stdout=PIPE, stderr=PIPE,
+    p = subprocess.Popen([FISH_BIN_PATH], stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                          env=env)
     out, err = p.communicate(text.encode('utf-8'))
     out = out.decode('utf-8', 'replace')
     err = err.decode('utf-8', 'replace')
-    return(out, err)
+    return out, err
 
 
 def escape_fish_cmd(text):
@@ -836,18 +837,18 @@ class FishConfigHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
 
     def do_remove_abbreviation(self, abbreviation):
         out, err = run_fish_cmd('abbr --erase %s' % abbreviation['word'])
-        if out or err:
+        if err:
             return err
         else:
-            return True
+            return None
 
     def do_save_abbreviation(self, abbreviation):
         out, err = run_fish_cmd('abbr --add \'%s\' \'%s\'' % (
             abbreviation['word'], abbreviation['phrase']))
-        if out or err:
-            return out
+        if err:
+            return err
         else:
-            return True
+            return None
 
     def secure_startswith(self, haystack, needle):
         if len(haystack) < len(needle):
@@ -975,17 +976,17 @@ class FishConfigHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
             else:
                 output = ["Unable to set prompt"]
         elif p == '/save_abbreviation/':
-            r = self.do_save_abbreviation(postvars)
-            if r:
-                output = ["OK"]
+            errmsg = self.do_save_abbreviation(postvars)
+            if errmsg:
+                output = [errmsg]
             else:
-                output = [r]
+                output = ["OK"]
         elif p == '/remove_abbreviation/':
-            r = self.do_remove_abbreviation(postvars)
-            if r:
-                output = ["OK"]
+            errmsg = self.do_remove_abbreviation(postvars)
+            if errmsg:
+                output = [errmsg]
             else:
-                output = [r]
+                output = ["OK"]
         else:
             return self.send_error(404)