templater: teach template loader to use open_template() function
The template loader can apparently load templates from relative paths,
so I needed to add that support to `open_template()`.
This takes the number of failing tests with PyOxidizer from 54 to 34.
Differential Revision: https://phab.mercurial-scm.org/D8907
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false