lib/how_is/sources/github.rb in how_is-23.0.0 vs lib/how_is/sources/github.rb in how_is-24.0.0

@@ -5,12 +5,27 @@
 require "github_api"
 require "okay/graphql"
 
 module HowIs
   module Sources
+    # Contains configuration information for GitHub-based sources.
     class Github
-      BASIC_AUTH    = ENV["HOWIS_BASIC_AUTH"]
-      ACCESS_TOKEN  = ENV["HOWIS_GITHUB_TOKEN"]
+      # An exception which is only raised if an environment variable
+      # is undefined.
+      class ConfigurationError < StandardError
+        def initialize(env_variable)
+          super("environment variable #{env_variable} not defined." \
+                  " See README.md for details.")
+        end
+      end
+
+      # A GitHub Personal Access Token.
+      ACCESS_TOKEN = ENV["HOWIS_GITHUB_TOKEN"]
+      raise ConfigurationError, "HOWIS_GITHUB_TOKEN" if ACCESS_TOKEN.nil?
+
+      # "<github username>:<personal access token>"
+      BASIC_AUTH = ENV["HOWIS_BASIC_AUTH"]
+      raise ConfigurationError, "HOWIS_BASIC_AUTH" if BASIC_AUTH.nil?
 
       # Used for the the Authorization header when talking to the
       # GitHub API.
       # https://developer.github.com/v4/guides/forming-calls/#communicating-with-graphql
       AUTHORIZATION_HEADER = "bearer " + ACCESS_TOKEN