show error for compile in progress

services/web/app/coffee/Features/Compile/ClsiManager.coffee

@@ -107,6 +107,8 @@ module.exports = ClsiManager =
 				callback null, compile:status:"project-too-large"
 			else if response.statusCode == 409
 				callback null, compile:status:"conflict"
+			else if response.statusCode == 423
+				callback null, compile:status:"compile-in-progress"
 			else
 				error = new Error("CLSI returned non-success code: #{response.statusCode}")
 				logger.error err: error, project_id: project_id, "CLSI returned failure code"

services/web/app/views/project/editor/pdf.pug

@@ -344,6 +344,10 @@ div.full-size.pdf(ng-controller="PdfController")
 				strong #{translate("pdf_compile_rate_limit_hit")} 
 				span #{translate("project_flagged_too_many_compiles")}
 
+			.alert.alert-danger(ng-show="pdf.compileInProgress")
+				strong #{translate("pdf_compile_in_progress_error")}
+				span #{translate("pdf_compile_try_again")}
+
 			.alert.alert-danger(ng-show="pdf.timedout")
 				p
 					strong #{translate("timedout")}. 

services/web/public/coffee/ide/pdf/controllers/PdfController.coffee

@@ -167,6 +167,7 @@ define [
 			$scope.pdf.compileTerminated = false
 			$scope.pdf.compileExited = false
 			$scope.pdf.failedCheck = false
+			$scope.pdf.compileInProgress = false
 
 			# make a cache to look up files by name
 			fileByPath = {}
@@ -223,6 +224,9 @@ define [
 			else if response.status == "validation-problems"
 				$scope.pdf.view = "validation-problems"
 				$scope.pdf.validation = response.validationProblems
+			else if response.status == "compile-in-progress"
+				$scope.pdf.view = 'errors'
+				$scope.pdf.compileInProgress = true
 			else if response.status == "success"
 				$scope.pdf.view = 'pdf'
 				$scope.shouldShowLogs = false