diff --git a/src/pydocstyle/cli.py b/src/pydocstyle/cli.py
index <HASH>..<HASH> 100644
--- a/src/pydocstyle/cli.py
+++ b/src/pydocstyle/cli.py
@@ -55,7 +55,7 @@ def run_pydocstyle(use_pep257=False):
 
     count = 0
     for error in errors:
-        sys.stderr.write('%s\n' % error)
+        sys.stdout.write('%s\n' % error)
         count += 1
     if count == 0:
         exit_code = ReturnCode.no_violations_found
diff --git a/src/pydocstyle/parser.py b/src/pydocstyle/parser.py
index <HASH>..<HASH> 100644
--- a/src/pydocstyle/parser.py
+++ b/src/pydocstyle/parser.py
@@ -380,8 +380,8 @@ class Parser(object):
         if self.current.value not in '([':
             raise AllError('Could not evaluate contents of __all__. ')
         if self.current.value == '[':
-            sys.stderr.write(
-                "{} WARNING: __all__ is defined as a list, this means "
+            sys.stdout.write(
+                "{0} WARNING: __all__ is defined as a list, this means "
                 "pydocstyle cannot reliably detect contents of the __all__ "
                 "variable, because it can be mutated. Change __all__ to be "
                 "an (immutable) tuple, to remove this warning. Note, "
changed stderr to stdout