Exception when upgrading to sasson 7.x-3.x-dev [#1825110]

When upgrading from Sasson 7.x-2.6 to Sasson 7.x-3.x-dev and try to load the site, I get the folowing PHP exception on the browser window. Are there any special upgrade instructions?

Additional uncaught exception thrown while handling exception.
Original

Assetic\Exception\FilterException: An error occurred while running: &#039;compass&#039; &#039;compile&#039; &#039;/tmp&#039; &#039;--output-style&#039; &#039;expanded&#039; &#039;--boring&#039; &#039;--images-dir&#039; &#039;/var/www/examle.com/beta/sites/all/themes/sasson/images&#039; &#039;--config&#039; &#039;/tmp/assetic_compass0NfsMY&#039; &#039;--sass-dir&#039; &#039;&#039; &#039;--css-dir&#039; &#039;&#039; &#039;/tmp/assetic_compassOme0bS.scss&#039; Error Output: sh: compass: not found Input: /* ############################################# * * ##### Sasson - advanced drupal theming. ##### * * ############################################# */ $overlay-opacity: 0.4; @import &quot;compass/css3&quot;; @import &quot;salsa/salsa&quot;; @import &quot;partials/overlay&quot;; @import &quot;partials/switch&quot;; // ==== Typography. ====================================== // Custom fonts from google web fonts // ======================================================= @if false { body { font-family: false , Arial, sans-serif; } } // ==== Design Overlay. ============================================= // Overlay a draggable image over the design for visual comparison // ================================================================== @if false { body.with-overlay #overlay-image { @extend %overlay; } // Overlay toggle switch .toggle-overlay { @extend %switch; top: 90px; } } // ==== Grid Background. ========================================= // Use CSS3 gradients to creat flexible background grid &quot;image&quot; // =============================================================== @if false { #page.grid-background { @include salsa-background; } // Grid toggle switch .toggle-grid { @extend %switch; } } in Assetic\Exception\FilterException::fromProcess() (line 40 of /var/www/example.com/beta/sites/all/themes/sasson/includes/assetic/src/Assetic/Exception/FilterException.php).
Additional

Assetic\Exception\FilterException: An error occurred while running: &#039;compass&#039; &#039;compile&#039; &#039;/tmp&#039; &#039;--output-style&#039; &#039;expanded&#039; &#039;--boring&#039; &#039;--images-dir&#039; &#039;/var/www/example.com/beta/sites/all/themes/sasson/images&#039; &#039;--config&#039; &#039;/tmp/assetic_compassuQJonF&#039; &#039;--sass-dir&#039; &#039;&#039; &#039;--css-dir&#039; &#039;&#039; &#039;/tmp/assetic_compassYK1bYy.scss&#039; Error Output: sh: compass: not found Input: /* ############################################# * * ##### Sasson - advanced drupal theming. ##### * * ############################################# */ $overlay-opacity: 0.4; @import &quot;compass/css3&quot;; @import &quot;salsa/salsa&quot;; @import &quot;partials/overlay&quot;; @import &quot;partials/switch&quot;; // ==== Typography. ====================================== // Custom fonts from google web fonts // ======================================================= @if false { body { font-family: false , Arial, sans-serif; } } // ==== Design Overlay. ============================================= // Overlay a draggable image over the design for visual comparison // ================================================================== @if false { body.with-overlay #overlay-image { @extend %overlay; } // Overlay toggle switch .toggle-overlay { @extend %switch; top: 90px; } } // ==== Grid Background. ========================================= // Use CSS3 gradients to creat flexible background grid &quot;image&quot; // =============================================================== @if false { #page.grid-background { @include salsa-background; } // Grid toggle switch .toggle-grid { @extend %switch; } } in Assetic\Exception\FilterException::fromProcess() (line 40 of /var/www/example.com/beta/sites/all/themes/sasson/includes/assetic/src/Assetic/Exception/FilterException.php).