Revert of Removed virtualenv from depot_tools

bootstrap/virtualenv/LICENSE.txt

Index: bootstrap/virtualenv/LICENSE.txt
diff --git a/bootstrap/virtualenv/LICENSE.txt b/bootstrap/virtualenv/LICENSE.txt
new file mode 100644
index 0000000000000000000000000000000000000000..7e00d5d512c2ae4007cecfe093c47bb6ced071bb
--- /dev/null
+++ b/bootstrap/virtualenv/LICENSE.txt
@@ -0,0 +1,22 @@
+Copyright (c) 2007 Ian Bicking and Contributors
+Copyright (c) 2009 Ian Bicking, The Open Planning Project
+Copyright (c) 2011-2014 The virtualenv developers
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.