Drush 7 fails UP command on D7 site- ?PEAR or D7 core problem

[AFowle]

I originally installed drush 6 via PEAR. Just upgraded to drush 7 via composer, without deleting drush 6 first. Upgrading a local dev version of a D7 site failed, as below. Reinstalling drush 6 via composer (after restoring site) then allowed upgrade to complete without error.

adrian@valerian:~> dr version
Drush Version : 7.0-dev

adrian@valerian:~> dr @bpnsdev up
Name Installed Version Proposed version Message
Views Data Export 7.x-3.0-beta7 7.x-3.0-beta8 Update available
(views_data_export)

Code updates will be made to the following projects: Views data export [views_data_export-7.x-3.0-beta8]

Note: A backup of your project will be stored to backups directory if it is not managed by a supported version control system.
Note: If you have made any modifications to any file that belongs to one of these projects, you will have to migrate those modifications after updating.
Do you really want to continue with the update process? (y/n): y
Project views_data_export was updated successfully. Installed version is now 7.x-3.0-beta8.
Backups were saved into the directory [ok]
/home/adrian/drush-backups/bpnsdev/20140919075600/modules/views_data_export.
Views_data_export 7301 Change the object cache table to support postgres
installations
Do you wish to run all pending updates? (y/n): y
require_once(/home/adrian/Drupaldev/bpnsdev/htdocs//core/includes/install.inc):[warning]
failed to open stream: No such file or directory core.drush.inc:1122
Drush command terminated abnormally due to an unrecoverable error. [error]
Error: require_once(): Failed opening required
'/home/adrian/Drupaldev/bpnsdev/htdocs//core/includes/install.inc'
(include_path='.:/usr/share/php5:/usr/share/php5/PEAR') in
/home/adrian/.composer/vendor/drush/drush/commands/core/core.drush.inc, line
1122
PHP Fatal error: require_once(): Failed opening required '/home/adrian/Drupaldev/bpnsdev/htdocs//core/includes/install.inc' (include_path='.:/usr/share/php5:/usr/share/php5/PEAR') in /home/adrian/.composer/vendor/drush/drush/commands/core/core.drush.inc on line 1122
The external command could not be executed due to an application error. [error]
'all' cache was cleared. [success]
Finished performing updates. [ok]

[jonhattan]

So drush is trying to include core/includes/install.inc in a D7 update.

It brokes here b45184a#diff-9e2b1896af01f89d4d97823474f12ae2R1122

[jonhattan]

Fixed in #839

[brylie]

I am getting this error frequently as well. How can I make sure I am running the correct version of Drush?

Failed opening required ...core/includes/install.inc