Raise clearer errors when configs are Missing (#48)

e.g. currently if SNOWFLAKE_PRIVATE_KEY and SNOWFLAKE_PRIVATE_KEY_PATH
are not set, the error message is:
```TypeError: no implicit conversion of nil into String```

Also: Update Gemfile.lock. It had gotten outdated.

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rb_snowflake_client (1.1.0)
+    rb_snowflake_client (1.1.1)
       concurrent-ruby (>= 1.2)
       connection_pool (>= 2.4)
       dotenv (>= 2.8)
@@ -50,17 +50,11 @@ PLATFORMS
 
 DEPENDENCIES
   bundler
-  concurrent-ruby
-  connection_pool
-  dotenv
-  jwt
-  oj
   parallel
   pry
   rake
   rb_snowflake_client!
-  retryable
   rspec
 
 BUNDLED WITH
-   2.5.4
+   2.5.10

lib/ruby_snowflake/client.rb

@@ -33,6 +33,7 @@ def initialize(details)
   class BadResponseError < Error ; end
   class ConnectionError < Error ; end
   class ConnectionStarvedError < Error ; end
+  class MissingConfig < Error ; end
   class RetryableBadResponseError < Error ; end
   class RequestError < Error ; end
   class QueryTimeoutError < Error ;  end
@@ -73,14 +74,21 @@ def self.from_env(logger: DEFAULT_LOGGER,
                       thread_scale_factor: env_option("SNOWFLAKE_THREAD_SCALE_FACTOR", DEFAULT_THREAD_SCALE_FACTOR),
                       http_retries: env_option("SNOWFLAKE_HTTP_RETRIES", DEFAULT_HTTP_RETRIES),
                       query_timeout: env_option("SNOWFLAKE_QUERY_TIMEOUT", DEFAULT_QUERY_TIMEOUT))
-      private_key = ENV["SNOWFLAKE_PRIVATE_KEY"] || File.read(ENV["SNOWFLAKE_PRIVATE_KEY_PATH"])
+      private_key =
+        if key = ENV["SNOWFLAKE_PRIVATE_KEY"]
+          key
+        elsif path = ENV["SNOWFLAKE_PRIVATE_KEY_PATH"]
+          File.read(path)
+        else
+          raise MissingConfig.new({}), "Either ENV['SNOWFLAKE_PRIVATE_KEY'] or ENV['SNOWFLAKE_PRIVATE_KEY_PATH'] must be set"
+        end
 
       new(
-        ENV["SNOWFLAKE_URI"],
+        ENV.fetch("SNOWFLAKE_URI"),
         private_key,
-        ENV["SNOWFLAKE_ORGANIZATION"],
-        ENV["SNOWFLAKE_ACCOUNT"],
-        ENV["SNOWFLAKE_USER"],
+        ENV.fetch("SNOWFLAKE_ORGANIZATION"),
+        ENV.fetch("SNOWFLAKE_ACCOUNT"),
+        ENV.fetch("SNOWFLAKE_USER"),
         ENV["SNOWFLAKE_DEFAULT_WAREHOUSE"],
         ENV["SNOWFLAKE_DEFAULT_DATABASE"],
         logger: logger,

spec/ruby_snowflake/client_spec.rb

@@ -3,6 +3,25 @@
 RSpec.describe RubySnowflake::Client do
   let(:client) { described_class.from_env }
 
+  describe "initialization" do
+    context "when the environment variables are not set" do
+      around do |example|
+        old_env = ENV.to_h
+
+        begin
+          ENV.clear
+          example.run
+        ensure
+          ENV.replace(old_env)
+        end
+      end
+
+      it "should raise an error" do
+        expect { client }.to raise_error(RubySnowflake::MissingConfig)
+      end
+    end
+  end
+
   describe "querying" do
     let(:query) { "" }
     let(:result) { client.query(query) }