Handle exec errors. Record failing command

in.js

@@ -64,12 +64,16 @@ process.stdin.on("data", stdin => {
         // TODO: We can generate an incredible amount of output for large repos.
         //  Stream this and check each line as it passes.
         if (stderr && stderr !== "") {
-            fail(new Error(stderr));
+            fail(new Error(stderr), cmdLine);
+        }
+
+        if(err) {
+            fail(err, cmdLine);
         }
 
         const lines = stdout.split('\n');
         if (lines.length <= 1) {
-            fail(new Error("no output from svn checkout"));
+            fail(new Error("no output from svn checkout"), cmdLine);
         }
 
         // "Checked out revision 47830."
@@ -78,7 +82,7 @@ process.stdin.on("data", stdin => {
         const revLine = lines[lines.length - 2];
         const header = "Checked out revision ";
         if (revLine.substr(0, header.length) !== header) {
-            fail(new Error('unexpected svn output.  expected revision, got "' + lines.slice(lines.length - 5).join("\n") + '"'));
+            fail(new Error('unexpected svn output.  expected revision, got "' + lines.slice(lines.length - 5).join("\n") + '"'), cmdLine);
         }
 
         const rev = revLine.substr(header.length, revLine.length - header.length - 2);

shared.js

@@ -5,7 +5,10 @@ function prettyJson(obj) {
 }
 exports.prettyJson = prettyJson;
 
-exports.fail = function fail(err) {
+exports.fail = function fail(err, cmd) {
+    if (cmd) {
+        console.error('Error while executing command:', filter_hidden(cmd));
+    }
     if (err) {
         console.error(filter_hidden(err.stack));
     }