Merge ~kissiel/checkbox-support:snap_utils into checkbox-support:master

[Maciej Kisielewski]

snap_utils: ensure values are stringified

if the value stored by the snapd is a string with only numbers in it, later on it gets printed in the json as number making python instantiate an Int from it.
Python's configparser expects only string, so this patch ensures the values are always treated as strings.

To test it, try setting any value to a number, and afterwards setting anything, like so:
$ sudo checkbox-snappy.configure FOO=123
$ sudo checkbox-snappy.configure FOO=bar
Traceback (most recent call last):
  File "/snap/checkbox-snappy/x1/bin/configure", line 30, in <module>
    main()
  File "/snap/checkbox-snappy/x1/bin/configure", line 27, in main
    update_configuration(vars_to_set)
  File "/snap/checkbox-snappy/x1/lib/python3.5/site-packages/checkbox_support/snap_utils/config.py", line 153, in update_configuration
    get_snapctl_config(list(get_configuration_set().keys())))
  File "/snap/checkbox-snappy/x1/lib/python3.5/site-packages/checkbox_support/snap_utils/config.py", line 115, in write_checkbox_conf
    config.set('environment', key, val)
  File "/snap/checkbox-snappy/x1/usr/lib/python3.5/configparser.py", line 1189, in set
    self._validate_value_types(option=option, value=value)
  File "/snap/checkbox-snappy/x1/usr/lib/python3.5/configparser.py", line 1174, in _validate_value_types
    raise TypeError("option values must be strings")
TypeError: option values must be strings

With this patch there should be no crash.

[Sylvain Pineau (sylvain-pineau)]

Good catch, +1

review: Approve

diff --git a/checkbox_support/snap_utils/config.py b/checkbox_support/snap_utils/config.py
index eb2b1aa..aaa7499 100644
--- a/checkbox_support/snap_utils/config.py
+++ b/checkbox_support/snap_utils/config.py
@@ -109,7 +109,7 @@ def write_checkbox_conf(configuration):
     config.optionxform = str
     config.add_section('environment')
     for key in sorted(configuration.keys()):
-        val = configuration[key]
+        val = str(configuration[key])
         # unmangle the key
         key = key.replace('-', '_').upper()
         config.set('environment', key, val)