4 files changed, 54 insertions, 5 deletions
diff --git a/lib/output/ebook.js b/lib/output/ebook.js
index 0cd1807..a74af41 100644
--- a/lib/output/ebook.js
+++ b/lib/output/ebook.js
@@ -5,6 +5,7 @@ var juice = require('juice');
 var command = require('../utils/command');
 var fs = require('../utils/fs');
 var Promise = require('../utils/promise');
+var error = require('../utils/error');
 var WebsiteOutput = require('./website');
 var assetsInliner = require('./assets-inliner');
 
@@ -59,12 +60,18 @@ EbookOutput.prototype.finish = function() {
         ].join(' ');
 
         return command.exec(cmd)
+        .progress(function(data) {
+            that.book.log.debug(data);
+        })
         .fail(function(err) {
             if (err.code == 127) {
-                err = new Error('Need to install ebook-convert from Calibre');
+                throw error.RequireInstallError({
+                    cmd: 'ebook-convert',
+                    install: 'Install it from Calibre: https://calibre-ebook.com'
+                });
             }
 
-            throw err;
+            throw error.EbookError(err);
         });
     });
 };
diff --git a/lib/utils/command.js b/lib/utils/command.js
index 49b0998..c1689cb 100644
--- a/lib/utils/command.js
+++ b/lib/utils/command.js
@@ -11,7 +11,26 @@ function exec(command, options) {
         return Promise.reject(new Error('Command execution is not possible on this platform'));
     }
 
-    return Promise.nfcall(childProcess.exec, command, options);
+    var d = Promise.defer();
+
+    var child = childProcess.exec(command, options, function(err, stdout, stderr) {
+        if (!err) {
+            d.resolve();
+        }
+
+        err.message = stdout.toString('utf8') + stderr.toString('utf8');
+        d.reject(err);
+    });
+
+    child.stdout.on('data', function (data) {
+        d.notify(data);
+    });
+
+    child.stderr.on('data', function (data) {
+        d.notify(data);
+    });
+
+    return d.promise;
 }
 
 // Spawn an executable
diff --git a/lib/utils/error.js b/lib/utils/error.js
index 52281bf..27fa59d 100644
--- a/lib/utils/error.js
+++ b/lib/utils/error.js
@@ -41,6 +41,15 @@ var FileOutOfScopeError = TypedError({
     code: 'EACCESS'
 });
 
+// A file is outside the scope
+var RequireInstallError = TypedError({
+    type: 'install.required',
+    message: '"{cmd}" is not installed.\n{install}',
+    cmd: null,
+    code: 'ENOENT',
+    install: ''
+});
+
 // Error for nunjucks templates
 var TemplateError = WrappedError({
     message: 'Error compiling template "{filename}": {origMessage}',
@@ -55,12 +64,19 @@ var PluginError = WrappedError({
     plugin: null
 });
 
-// Error for nunjucks templates
+// Error with the book's configuration
 var ConfigurationError = WrappedError({
     message: 'Error with book\'s configuration: {origMessage}',
     type: 'configuration'
 });
 
+// Error during ebook generation
+var EbookError = WrappedError({
+    message: 'Error during ebook generation: {origMessage}\n{stdout}',
+    type: 'ebook',
+    stdout: ''
+});
+
 // Deprecate methods/fields
 function deprecateMethod(fn, msg) {
     return deprecated.method(msg, log.warn.ln, fn);
@@ -74,6 +90,7 @@ module.exports = {
 
     ParsingError: ParsingError,
     OutputError: OutputError,
+    RequireInstallError: RequireInstallError,
 
     FileNotFoundError: FileNotFoundError,
     FileOutOfScopeError: FileOutOfScopeError,
@@ -81,6 +98,7 @@ module.exports = {
     TemplateError: TemplateError,
     PluginError: PluginError,
     ConfigurationError: ConfigurationError,
+    EbookError: EbookError,
 
     deprecateMethod: deprecateMethod,
     deprecateField: deprecateField
diff --git a/lib/utils/images.js b/lib/utils/images.js
index 8169b06..44356a1 100644
--- a/lib/utils/images.js
+++ b/lib/utils/images.js
@@ -10,7 +10,12 @@ function convertSVGToPNG(source, dest, options) {
 
     return command.spawn('svgexport', [source, dest])
     .fail(function(err) {
-        if (err.code == 'ENOENT') err = new Error('Need to install "svgexport" using "npm install svgexport -g"');
+        if (err.code == 'ENOENT') {
+            error.RequireInstallError({
+                cmd: 'svgexport',
+                install: 'Install it using: "npm install svgexport -g"'
+            });
+        }
         throw err;
     })
     .then(function() {