diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -110,6 +110,7 @@ pypats = [
     (r'.{85}', "line too long"),
     (r'.{81}', "warning: line over 80 characters"),
     (r'[^\n]\Z', "no trailing newline"),
+    (r'(\S\s+|^\s+)\n', "trailing whitespace"),
 #    (r'^\s+[^_ ][^_. ]+_[^_]+\s*=', "don't use underbars in identifiers"),
 #    (r'\w*[a-z][A-Z]\w*\s*=', "don't use camelcase in identifiers"),
     (r'^\s*(if|while|def|class|except|try)\s[^[]*:\s*[^\]#\s]+',
diff --git a/hgext/convert/subversion.py b/hgext/convert/subversion.py
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -651,7 +651,7 @@ class svn_source(converter_source):
                 else:
                     self.ui.debug('unknown path in revision %d: %s\n' % \
                                   (revnum, path))
-            elif kind == svn.core.svn_node_dir:                
+            elif kind == svn.core.svn_node_dir:
                 if ent.action == 'M':
                     # If the directory just had a prop change,
                     # then we shouldn't need to look for its children.
@@ -823,7 +823,7 @@ class svn_source(converter_source):
     def getfile(self, file, rev):
         # TODO: ra.get_file transmits the whole file instead of diffs.
         if file in self.removed:
-            raise IOError()         
+            raise IOError()
         mode = ''
         try:
             new_module, revnum = self.revsplit(rev)[1:]
@@ -892,7 +892,7 @@ class svn_source(converter_source):
         finally:
             if module is not None:
                 self.reparent(prevmodule)
-    
+
     def _getlog(self, paths, start, end, limit=0, discover_changed_paths=True,
                 strict_node_history=False):
         # Normalize path names, svn >= 1.5 only wants paths relative to
diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -407,7 +407,7 @@ def runcommand(lui, repo, cmd, fullargs,
 
 def _getlocal(ui, rpath):
     """Return (path, local ui object) for the given target path.
-    
+
     Takes paths in [cwd]/.hg/hgrc into account."
     """
     try:
diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -15,7 +15,7 @@ def _getpreferredencoding():
     for Python 2.7 and up. This is the same corrected code for earlier
     Python versions.
 
-    However, we can't use a version check for this method, as some distributions 
+    However, we can't use a version check for this method, as some distributions
     patch Python to fix this. Instead, we use it as a 'fixer' for the mac-roman
     encoding, as it is unlikely that this encoding is the actually expected.
     '''
diff --git a/mercurial/subrepo.py b/mercurial/subrepo.py
--- a/mercurial/subrepo.py
+++ b/mercurial/subrepo.py
@@ -192,7 +192,7 @@ def _abssource(repo, push=False, abort=T
         if repo.ui.config('paths', 'default'):
             return repo.ui.config('paths', 'default')
     if abort:
-        raise util.Abort(_("default path for subrepository %s not found") % 
+        raise util.Abort(_("default path for subrepository %s not found") %
             reporelpath(repo))
 
 def itersubrepos(ctx1, ctx2):
diff --git a/mercurial/url.py b/mercurial/url.py
--- a/mercurial/url.py
+++ b/mercurial/url.py
@@ -489,7 +489,7 @@ class httphandler(keepalive.HTTPHandler)
 def _verifycert(cert, hostname):
     '''Verify that cert (in socket.getpeercert() format) matches hostname.
     CRLs and subjectAltName are not handled.
-    
+
     Returns error message if any problems are found and None on success.
     '''
     if not cert: