make display plugin checksum error to user

The error follows a generic message, so can be ignored by users who may
not understand the implications.

backend/local/backend.go

@@ -412,20 +412,18 @@ func (b *Local) stateWorkspaceDir() string {
 func (b *Local) pluginInitRequired(providerErr *terraform.ResourceProviderError) {
 	b.CLI.Output(b.Colorize().Color(fmt.Sprintf(
 		strings.TrimSpace(errPluginInit)+"\n",
-		"Could not satisfy plugin requirements",
 		providerErr)))
 }
 
+// this relies on multierror to format the plugin errors below the copy
 const errPluginInit = `
 [reset][bold][yellow]Plugin reinitialization required. Please run "terraform init".[reset]
-[yellow]Reason: %s
+[yellow]Reason: Could not satisfy plugin requirements.
 
 Plugins are external binaries that Terraform uses to access and manipulate
 resources. If this message is showing up, it means that the configuration you
 have references plugins which can't be located, don't satisfy the version
 constraints, or are otherwise incompatible.
 
-The errors encountered discovering plugins are:
-
-%s
+[reset][red]%s
 `

command/plugins.go

@@ -53,12 +53,7 @@ func (r *multiVersionProviderResolver) ResolveProviders(
 				continue
 			}
 			if !reqd[name].AcceptsSHA256(digest) {
-				// This generic error message is intended to avoid troubling
-				// users with implementation details. The main useful point
-				// here is that they need to run "terraform init" to
-				// fix this, which is covered by the UI code reporting these
-				// error messages.
-				errs = append(errs, fmt.Errorf("provider.%s: installed but not yet initialized", name))
+				errs = append(errs, fmt.Errorf("provider.%s: checksum mismatch", name))
 				continue
 			}