Fix exception when soap:Fault contains invalid encoding (#923)

Co-authored-by: David Escala <descala@ingent.net>

lib/savon/soap_fault.rb

@@ -3,7 +3,14 @@ module Savon
   class SOAPFault < Error
 
     def self.present?(http, xml = nil)
-      xml ||= http.body
+      xml_orig ||= http.body
+      if xml_orig.valid_encoding?
+        xml = xml_orig
+      else
+        xml = xml_orig.encode(
+          'UTF-8', "ISO-8859-1", invalid: :replace, undef: :replace, replace: ''
+        )
+      end
       fault_node  = xml.include?("Fault>")
       soap1_fault = xml.match(/faultcode\/?\>/) && xml.match(/faultstring\/?\>/)
       soap2_fault = xml.include?("Code>") && xml.include?("Reason>")

spec/fixtures/response/soap_fault_invalid_encoding.xml

@@ -0,0 +1,8 @@
+<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
+   <soap:Body>
+      <soap:Fault>
+         <faultcode>soap:Server</faultcode>
+         <faultstring>Response with invalid encoding ñ ñ</faultstring>
+      </soap:Fault>
+   </soap:Body>
+</soap:Envelope>

spec/savon/soap_fault_spec.rb

@@ -49,6 +49,11 @@
     it "returns false unless the HTTP response contains a SOAP fault" do
       expect(Savon::SOAPFault.present? new_response).to be_falsey
     end
+
+    it "returns true even if the HTTP response contains a SOAP fault with invalid encoding" do
+      http = new_response(:body => Fixture.response(:soap_fault_invalid_encoding))
+      expect(Savon::SOAPFault.present? http).to be_truthy
+    end
   end
 
   [:message, :to_s].each do |method|