Fix string encoding in compiler and compressor errors.

The errors raised when a compiler or compressor failed were including
the message as bytes instead of str. This meant that when printing the
errors, or seeing them in the django-pipeline-error element that's
rendered to the page, the error would be shown as the repr of the
bytestring (which did not properly show newlines, and included extra b''
junk). This change fixes things to decode to str when appropriate.

Author: davidt

pipeline/compilers/__init__.py

@@ -6,6 +6,7 @@
 from django.contrib.staticfiles import finders
 from django.contrib.staticfiles.storage import staticfiles_storage
 from django.core.files.base import ContentFile
+from django.utils.encoding import force_str
 
 from pipeline.conf import settings
 from pipeline.exceptions import CompilerError
@@ -119,7 +120,8 @@ def execute_command(self, command, cwd=None, stdout_captured=None):
             # We always catch stdout in a file, but we may not have a use for it.
             temp_file_container = cwd or os.path.dirname(stdout_captured or "") or os.getcwd()
             with NamedTemporaryFile('wb', delete=False, dir=temp_file_container) as stdout:
-                compiling = subprocess.Popen(argument_list, cwd=cwd,
+                compiling = subprocess.Popen(argument_list,
+                                             cwd=cwd,
                                              stdout=stdout,
                                              stderr=subprocess.PIPE)
                 _, stderr = compiling.communicate()
@@ -130,7 +132,7 @@ def execute_command(self, command, cwd=None, stdout_captured=None):
                 raise CompilerError(
                     f"{argument_list!r} exit code {compiling.returncode}\n{stderr}",
                     command=argument_list,
-                    error_output=stderr)
+                    error_output=force_str(stderr))
 
             # User wants to see everything that happened.
             if self.verbose:

pipeline/compressors/__init__.py

@@ -240,16 +240,18 @@ def execute_command(self, command, content):
             else:
                 argument_list.extend(flattening_arg)
 
-        pipe = subprocess.Popen(argument_list, stdout=subprocess.PIPE,
-                                stdin=subprocess.PIPE, stderr=subprocess.PIPE)
+        pipe = subprocess.Popen(argument_list,
+                                stdout=subprocess.PIPE,
+                                stdin=subprocess.PIPE,
+                                stderr=subprocess.PIPE)
         if content:
             content = smart_bytes(content)
         stdout, stderr = pipe.communicate(content)
         set_std_streams_blocking()
         if stderr.strip() and pipe.returncode != 0:
-            raise CompressorError(stderr)
+            raise CompressorError(force_str(stderr))
         elif self.verbose:
-            print(stderr)
+            print(force_str(stderr))
         return force_str(stdout)