Leak less files during test.

Tracks all created files and destroy them all during teardown.
Otherwise multiple call to mktmp would leak previously unclosed files.

This should really ideally be a context manager and be tracked better.

IPython/testing/tools.py

@@ -270,16 +270,21 b' class TempFileMixin(object):'
     def mktmp(self, src, ext='.py'):
         """Make a valid python temp file."""
         fname, f = temp_pyfile(src, ext)
-        self.tmpfile = f
+        if not hasattr(self, 'tmps'):
+            self.tmps=[]
+        self.tmps.append((f, fname))
         self.fname = fname
 
     def tearDown(self):
-        if hasattr(self, 'tmpfile'):
             # If the tmpfile wasn't made because of skipped tests, like in
             # win32, there's nothing to cleanup.
-            self.tmpfile.close()
+        if hasattr(self, 'tmps'):
+            for f,fname in self.tmps:
+                # If the tmpfile wasn't made because of skipped tests, like in
+                # win32, there's nothing to cleanup.
+                f.close()
             try:
-                os.unlink(self.fname)
+                    os.unlink(fname)
             except:
                 # On Windows, even though we close the file, we still can't
                 # delete it.  I have no clue why