Parallelize compressors

optimage.py

@@ -16,6 +16,7 @@
 import collections
 import contextlib
 import logging
+import multiprocessing.pool
 import os
 import os.path
 import shutil
@@ -173,9 +174,15 @@ def _compress_with(input_filename, output_filename, compressors):
     input.
     """
     with _temporary_filenames(len(compressors)) as temp_filenames:
-        results = []
-        for compressor, temp_filename in zip(compressors, temp_filenames):
-            results.append(_process(compressor, input_filename, temp_filename))
+        process_args = [
+            (compressor, input_filename, temp_filename)
+            for compressor, temp_filename in zip(compressors, temp_filenames)
+        ]
+        process_unpack = lambda args: _process(*args)
+        results = multiprocessing.pool.ThreadPool().map(process_unpack,
+                                                        process_args,
+                                                        chunksize=1)
+
         best_result = min(results)
         os.rename(best_result.filename, output_filename)
 

setup.py

@@ -29,7 +29,7 @@
     scripts=['scripts/optimage'],
     setup_requires=['pytest-runner'],
     install_requires=['Pillow'],
-    tests_require=['pytest', 'pytest-cov', 'pytest-catchlog'],
+    tests_require=['pytest>=3.3', 'pytest-cov'],
     classifiers=[
         'Development Status :: 3 - Alpha',
         'Environment :: Console',

test_optimage_e2e.py

@@ -3,11 +3,6 @@
 import subprocess
 
 import pytest
-try:
-  import pytest_catchlog
-  catchlog_available = True
-except ImportError:
-  catchlog_available = False
 
 import optimage
 
@@ -147,8 +142,6 @@ def mock_check_output(args, stderr=None):
     assert 'Output:\ncustom error' in err
 
 
-@pytest.mark.skipif(not catchlog_available,
-                    reason='pytest_catchlog not available')
 @pytest.mark.parametrize('filename, compressor', [
     # Do not specify compressor as it depends on the version of the commands
     # installed. In Mac I get that pngcrush is better than zopflipng, but not in