Run auto-spell-checker (codespell) on files in depot_tools.

This should only change spelling in:
 - messages that are printed
 - comments
 - docstrings

Review-Url: https://codereview.chromium.org/2277513002
diff --git a/git_cl.py b/git_cl.py
index 9db5f35..5831b12 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -202,7 +202,7 @@
     branch = GetCurrentBranch()
     assert branch, 'a branch name OR currently checked out branch is required'
   args = ['config']
-  # Check for boolean first, becuase bool is int, but int is not bool.
+  # Check for boolean first, because bool is int, but int is not bool.
   if value is None:
     args.append('--unset')
   elif isinstance(value, bool):
@@ -2403,7 +2403,7 @@
     if not('From Gerrit Code Review' in data and 'add_ChangeId()' in data):
       return
     print('Warning: you have Gerrit commit-msg hook installed.\n'
-          'It is not neccessary for uploading with git cl in squash mode, '
+          'It is not necessary for uploading with git cl in squash mode, '
           'and may interfere with it in subtle ways.\n'
           'We recommend you remove the commit-msg hook.')
     if offer_removal:
@@ -3114,7 +3114,7 @@
 
   See GetStatus() for a list of possible statuses.
   """
-  # Silence upload.py otherwise it becomes unwieldly.
+  # Silence upload.py otherwise it becomes unwieldy.
   upload.verbosity = 0
 
   if fine_grained: