Ignore invalid versions in the forge, ie. 0.5.0-rc1

Instead of failing completely

features/install.feature

@@ -27,6 +27,18 @@ Feature: cli/install
     And the file "modules/apt/Modulefile" should match /version *'0\.0\.4'/
     And the file "modules/stdlib/Modulefile" should match /name *'puppetlabs-stdlib'/
 
+  Scenario: Installing a module with invalid versions in the forge
+    Given a file named "Puppetfile" with:
+    """
+    forge "http://forge.puppetlabs.com"
+
+    mod 'puppetlabs/apache', '0.4.0'
+    """
+    When I run `librarian-puppet install`
+    Then the exit status should be 0
+    And the file "modules/apache/Modulefile" should match /name *'puppetlabs-apache'/
+    And the file "modules/apache/Modulefile" should match /version *'0\.4\.0'/
+
   Scenario: Installing a module with several constraints
     Given a file named "Puppetfile" with:
     """

lib/librarian/puppet/source/forge.rb

@@ -22,7 +22,9 @@ def versions
               raise Error, "Unable to find module '#{name}' on #{source}"
             end
 
-            data['releases'].map { |r| r['version'] }.sort.reverse
+            versions = data['releases'].map { |r| r['version'] }.sort.reverse
+            versions.select { |v| ! Gem::Version.correct? v }.each { |v| debug { "Ignoring invalid version '#{v}' for module #{name}" } }
+            versions.select { |v| Gem::Version.correct? v }
           end
 
           def dependencies(version)
@@ -104,7 +106,6 @@ def cache_version_unpacked!(version)
               path.unlink
               raise Error, "Error executing puppet module install:\n#{command}\nError:\n#{output}"
             end
-
           end
 
           def check_puppet_module_options
@@ -148,6 +149,10 @@ def stream(file, &block)
             end
           end
 
+          def debug(*args, &block)
+            environment.logger.debug(*args, &block)
+          end
+
         private
 
           def api_call(path)