diff --git a/commands/preprocess_cssless.py b/commands/preprocess_cssless.py

index 0c29d96..94edc3f 100644

--- a/commands/preprocess_cssless.py

+++ b/commands/preprocess_cssless.py

@@ -19,0 +20 @@ import functools

+import inspect

@@ -28 +28,0 @@ from lxml.etree import strip_elements

-import premailer

@@ -31,2 +31,21 @@ from premailer import Premailer

-premailer_version = premailer.__version__.split('.')

-premailer_is_new=len(premailer_version) >= 2 and int(premailer_version[0]) >= 3 and int(premailer_version[1]) >= 9

+

+def premailer_options(src_path):

+ options = {

+ 'base_url': src_path,

+ 'disable_link_rewrites': True,

+ 'remove_classes': True,

+ }

+ parameters = inspect.signature(Premailer.__init__).parameters

+ if 'allow_loading_external_files' in parameters:

+ options['allow_loading_external_files'] = True

+ if 'disable_leftover_css' in parameters:

+ options['disable_leftover_css'] = True

+ return options

+

+

+class CsslessPremailer(Premailer):

+ def _css_rules_to_string(self, rules):

+ # Leftover CSS is stripped after inlining. Premailer 3.7 can crash

+ # serializing nested @media leftovers, so keep the cssless pass empty.

+ return ''

+

@@ -78,7 +97 @@ def preprocess_html_merge_css(root, src_path):

- if premailer_is_new:

- premailer = Premailer(root, base_url=src_path,

- disable_link_rewrites=True, remove_classes=True,

- allow_loading_external_files=True)

- else:

- premailer = Premailer(root, base_url=src_path,

- disable_link_rewrites=True, remove_classes=True)

+ premailer = CsslessPremailer(root, **premailer_options(src_path))

diff --git a/preprocess_qch.py b/preprocess_qch.py

index 856afb5..ea97aba 100755

--- a/preprocess_qch.py

+++ b/preprocess_qch.py

@@ -66,0 +67 @@ def main():

+ src_path, dst_path = paths_list[i]

@@ -68,2 +69,7 @@ def main():

- i, len(paths_list), paths_list[i][1]))

- output = future.result()

+ i, len(paths_list), dst_path))

+ try:

+ output = future.result()

+ except Exception as exc:

+ raise RuntimeError(

+ 'failed to preprocess {} -> {}'.format(

+ src_path, dst_path)) from exc