Fix logging the fallback to the full index on GemspecError's

The debug message suggests retrying using `--full-index`, but the retry
is happening automatically. Just log that we are falling back to the
full index, like we do with other errors.

lib/bundler/fetcher/dependency.rb

@@ -34,14 +34,10 @@ module Bundler
 
         returned_gems = spec_list.map(&:first).uniq
         specs(deps_list, full_dependency_list + returned_gems, spec_list + last_spec_list)
-      rescue MarshalError
+      rescue MarshalError, HTTPError, GemspecError
         Bundler.ui.info "" unless Bundler.ui.debug? # new line now that the dots are over
         Bundler.ui.debug "could not fetch from the dependency API, trying the full index"
         nil
-      rescue HTTPError, GemspecError
-        Bundler.ui.info "" unless Bundler.ui.debug? # new line now that the dots are over
-        Bundler.ui.debug "could not fetch from the dependency API\nit's suggested to retry using the full index via `bundle install --full-index`"
-        nil
       end
 
       def dependency_specs(gem_names)

spec/bundler/bundler/fetcher/dependency_spec.rb

@@ -155,9 +155,9 @@ RSpec.describe Bundler::Fetcher::Dependency do
       end
     end
 
-    shared_examples_for "the error suggests retrying with the full index" do
-      it "should log the inability to fetch from API at debug level" do
-        expect(Bundler).to receive_message_chain(:ui, :debug).with("could not fetch from the dependency API\nit's suggested to retry using the full index via `bundle install --full-index`")
+    shared_examples_for "the error is logged" do
+      it "should log the inability to fetch from API at debug level, and mention retrying" do
+        expect(Bundler).to receive_message_chain(:ui, :debug).with("could not fetch from the dependency API, trying the full index")
         subject.specs(gem_names, full_dependency_list, last_spec_list)
       end
     end
@@ -166,25 +166,21 @@ RSpec.describe Bundler::Fetcher::Dependency do
       before { allow(subject).to receive(:dependency_specs) { raise Bundler::HTTPError.new } }
 
       it_behaves_like "the error is properly handled"
-      it_behaves_like "the error suggests retrying with the full index"
+      it_behaves_like "the error is logged"
     end
 
     context "when a GemspecError occurs" do
       before { allow(subject).to receive(:dependency_specs) { raise Bundler::GemspecError.new } }
 
       it_behaves_like "the error is properly handled"
-      it_behaves_like "the error suggests retrying with the full index"
+      it_behaves_like "the error is logged"
     end
 
     context "when a MarshalError occurs" do
       before { allow(subject).to receive(:dependency_specs) { raise Bundler::MarshalError.new } }
 
       it_behaves_like "the error is properly handled"
-
-      it "should log the inability to fetch from API and mention retrying" do
-        expect(Bundler).to receive_message_chain(:ui, :debug).with("could not fetch from the dependency API, trying the full index")
-        subject.specs(gem_names, full_dependency_list, last_spec_list)
-      end
+      it_behaves_like "the error is logged"
     end
   end