Trisquel Sugar default activities doesn't start up

Many default sugar activities like Browser, Memorize, Slider-Puzzle not start up and looks like the problem is related to missing dependencies, also *sugar-firefox-activity* that is not a default activity but available in the repository install icecat but not start because still require firefox.

logs:

```
** (sugar-activity:25358): WARNING **: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided b>
Traceback (most recent call last):
File "/usr/bin/sugar-activity", line 219, in
main()
File "/usr/bin/sugar-activity", line 163, in main
module = __import__(module_name)
File "/home/ami/Activities/Browse.activity/webactivity.py", line 62, in
from collabwrapper import CollabWrapper
File "/home/ami/Activities/Browse.activity/collabwrapper.py", line 72, in
gi.require_version('TelepathyGLib', '0.12')
File "/usr/lib/python2.7/dist-packages/gi/__init__.py", line 102, in require_version
raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace TelepathyGLib not available
Exited with status 1, pid 25358 data (', mode 'w' at 0x7fa4679fec00>, '73b54ea894cf9fb773f5a7848625f1b6fd443e63')

```

Trisquel 8.0 support ended in April 2021.
Please open a new issue in case it remains on the current supported release.

Cheers!