provider is not found.
Previously a user would see the following error even if terraform was
only searching the local filesystem:
"provider registry registry.terraform.io does not have a provider named
...."
This PR adds a registry-specific error type and modifies the MultiSource
installer to check for registry errors. It will return the
registry-specific error message if there is one, but if not the error
message will list all locations searched.
An earlier commit added a redundant stub for a new network mirror source
that was already previously stubbed as HTTPMirrorSource.
This commit removes the unnecessary extra stub and changes the CLI config
handling to use it instead. Along the way this also switches to using a
full base URL rather than just a hostname for the mirror, because using
the usual "Terraform-native service discovery" protocol here doesn't isn't
as useful as in the places we normally use it (the mirror mechanism is
already serving as an indirection over the registry protocol) and using
a direct base URL will make it easier to deploy an HTTP mirror under
a path prefix on an existing static file server.
In a future commit, these implementations of Source will allow finding
and retrieving provider packages via local mirrors, both in the local
filesystem and over the network using an HTTP-based protocol.
Kristin Laemmert