Vim plugin: don't clobber text if yapf command returned error
Check yapf command exit code. If there was an error, show error message
with the last line of output and don't change text in a buffer.
diff --git a/CHANGELOG b/CHANGELOG
index 62ca8a4..cf46f29 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -9,6 +9,7 @@
### Fixed
- Corrected how `DEDENT_CLOSING_BRACKETS` and `COALESCE_BRACKETS` interacted.
- Fix return value to return a boolean.
+- Correct vim plugin not to clobber edited code if yapf returns an error.
## [0.16.3] 2017-07-13
### Changed
