Open our output file in append mode alwaysbug/193

This avoid overwriting portions of our log output when using Flake8
in verbose mode.

Closes #193

2 files changed, 7 insertions, 1 deletions

diff --git a/docs/source/release-notes/3.0.3.rst b/docs/source/release-notes/3.0.3.rst
index 0361879..1c23c8e 100644
--- a/docs/source/release-notes/3.0.3.rst
+++ b/docs/source/release-notes/3.0.3.rst
@@ -10,9 +10,15 @@
 - Fix issue where users were unable to ignore plugin errors that were on
   by default. (See also `GitLab#195`_)
 
+- Always open our output file in append mode so we do not overwrite log
+  messages. (See also `GitLab#193`_)
+
+
 .. links
 .. _GitLab#178:
     https://gitlab.com/pycqa/flake8/issues/178
+.. _GitLab#193:
+    https://gitlab.com/pycqa/flake8/issues/193
 .. _GitLab#195:
     https://gitlab.com/pycqa/flake8/issues/195
 
diff --git a/src/flake8/formatting/base.py b/src/flake8/formatting/base.py
index 336bf50..97c60e1 100644
--- a/src/flake8/formatting/base.py
+++ b/src/flake8/formatting/base.py
@@ -50,7 +50,7 @@ class BaseFormatter(object):
         This defaults to initializing :attr:`output_fd` if :attr:`filename`
         """
         if self.filename:
-            self.output_fd = open(self.filename, 'w')
+            self.output_fd = open(self.filename, 'a')
 
     def handle(self, error):
         """Handle an error reported by Flake8.