[BuildStream] Heads Up

[William Salmon <will salmon codethink co uk>]

We have recently bumped the required version of click for bst.

If build stream has been installed the recommended way via a package 
manger, be that pip or your OS's then you should not have any issues at all!

If you have a older version installed from source via pips editable 
install and checked out the latest master but have a old version of 
click installed you will get a cryptic error message:

Traceback (most recent call last):
  File "/home/will/.local/bin/bst", line 5, in <module>
    from buildstream._frontend import cli
  File 
"/home/will/projects/buildstream/buildstream/buildstream/_frontend/__init__.py", 
line 20, in <module>
    from .cli import cli
  File 
"/home/will/projects/buildstream/buildstream/buildstream/_frontend/cli.py", 
line 1088, in <module>
    @click.pass_obj
  File "/home/will/.local/lib/python3.5/site-packages/click/core.py", 
line 1163, in decorator
    cmd = command(*args, **kwargs)(f)
  File 
"/home/will/.local/lib/python3.5/site-packages/click/decorators.py", 
line 115, in decorator
    cmd = _make_command(f, name, attrs, cls)
  File 
"/home/will/.local/lib/python3.5/site-packages/click/decorators.py", 
line 89, in _make_command
    callback=f, params=params, **attrs)
TypeError: __init__() got an unexpected keyword argument 'hidden'

You may need to trigger pip to update your version of pip

if you installed via: `pip install --user -e .` like i did.

Then you can just rerun the command in the buildstream folder.

We have a good install guide on the web site but if anyone needs their 
memory jogging like I did then I hope you found this email as useful as 
i would have!

Will