hgweb: propagate http headers from ErrorResponse for web interface commands
This makes it possible for e.g. authorization hooks to provide appropriate
headers to make the web browser ask for credentials.
It's done in the same way as the existing code in wireprotoserver.py.
# 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