only treat stderr as text after getting non-zero exit code, otherwise it should be pdf binary data

alanhamlett · alanhamlett · commit bac0816fa90b · 2017-05-04T00:06:00.000-07:00
diff --git a/pdfkit/pdfkit.py b/pdfkit/pdfkit.py
@@ -140,23 +140,25 @@ def to_pdf(self, path=None):
             input = None
         stdout, stderr = result.communicate(input=input)
         stderr = stderr or stdout
-        try:
-            stderr = stderr.decode('utf-8')
-        except UnicodeDecodeError:
-            stderr = ''
+
         exit_code = result.returncode
+        if exit_code != 0:
+            try:
+                stderr = stderr.decode('utf-8')
+            except UnicodeDecodeError:
+                stderr = ''
 
-        if 'cannot connect to X server' in stderr:
-            raise IOError('%s\n'
-                          'You will need to run wkhtmltopdf within a "virtual" X server.\n'
-                          'Go to the link below for more information\n'
-                          'https://github.com/JazzCore/python-pdfkit/wiki/Using-wkhtmltopdf-without-X-server' % stderr)
+            if 'cannot connect to X server' in stderr:
+                raise IOError('%s\n'
+                            'You will need to run wkhtmltopdf within a "virtual" X server.\n'
+                            'Go to the link below for more information\n'
+                            'https://github.com/JazzCore/python-pdfkit/wiki/Using-wkhtmltopdf-without-X-server' % stderr)
 
-        if 'Error' in stderr:
-            raise IOError('wkhtmltopdf reported an error:\n' + stderr)
+            if 'Error' in stderr:
+                raise IOError('wkhtmltopdf reported an error:\n' + stderr)
 
-        if exit_code != 0:
-            raise IOError("wkhtmltopdf exited with non-zero code {0}. error:\n{1}".format(exit_code, stderr))
+            error_msg = stderr or 'Unknown Error'
+            raise IOError("wkhtmltopdf exited with non-zero code {0}. error:\n{1}".format(exit_code, error_msg))
 
         # Since wkhtmltopdf sends its output to stderr we will capture it
         # and properly send to stdout
