In mixed-line-endings, move check/print to main() as suggested by asottile (PR 341)

pre_commit_hooks/mixed_line_ending.py

diff --git a/pre_commit_hooks/mixed_line_ending.py b/pre_commit_hooks/mixed_line_ending.py
index cd0c125..e35a65c 100644
--- a/pre_commit_hooks/mixed_line_ending.py
+++ b/pre_commit_hooks/mixed_line_ending.py
@@ -37,15 +37,9 @@
     # Some amount of mixed line endings
     mixed = sum(bool(x) for x in counts.values()) > 1
 
-    if fix == 'no':
-        if mixed:
-            # Not fixing, just report problematic file
-            print('Mixed line endings: {filename}'.format(filename=filename))
+    if fix == 'no' or (fix == 'auto' and not mixed):
         return mixed
 
-    if fix == 'auto' and not mixed:
-        return False
-
     if fix == 'auto':
         max_ending = LF
         max_lines = 0
@@ -82,7 +76,12 @@
 
     retv = 0
     for filename in args.filenames:
-        retv |= fix_filename(filename, args.fix)
+        if fix_filename(filename, args.fix):
+            if args.fix == 'no':
+                print('{}: mixed line endings'.format(filename))
+            else:
+                print('{}: fixed mixed line endings'.format(filename))
+            retv = 1
     return retv