[Bugs] #3707 sugar UNSP: Bundle registry file monitoring clashes with its own operations

[Sugar Labs Bugs]

#3707: Bundle registry file monitoring clashes with its own operations
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    Reporter:  dsd                        |          Owner:  erikos                     
        Type:  defect                     |         Status:  new                        
    Priority:  Unspecified by Maintainer  |      Milestone:  Unspecified by Release Team
   Component:  sugar                      |        Version:  Unspecified                
    Severity:  Unspecified                |       Keywords:                             
Distribution:  Unspecified                |   Status_field:  Unconfirmed                
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 There are several races within bundleregistry.py because the gio file
 monitor does not collaborate with the install/remove/upgrade operations in
 the file.

 For example, on an upgrade, the code first uninstalls the old version (by
 deleting the whole activity dir tree) and then calling
 self.remove_bundle() to remove it from self._bundles. However, the file
 monitor will *also* notice the file deletion (uninstallation) and call
 self.remove_bundle. One of the two will fail.

 Then, continuing with the upgrade, install() is called to install the new
 bundle, first unpacking the bundle and then calling self.add_bundle().
 However, during the unpack, the file monitor will also note the presence
 of the new activity and call self.add_bundle(). One of the two calls will
 fail as the bundle is already present.

 I suspect this is the cause of http://dev.laptop.org/ticket/11373

 This behaviour can be seen by sprinkling a few debug log messages in
 bundleregistry.py then upgrading an activity via the journal or the
 activity updater.

 Reproduced with sugar-0.96.3.

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Ticket URL: <http://bugs.sugarlabs.org/ticket/3707>
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