Merge pull request #8 from jhermann/patch-1

Better reporting of command failures

dephell_setuptools/_cmd.py

@@ -60,7 +60,12 @@ def content(self) -> Dict[str, Any]:
                     env=env,
                 )
             if result.returncode != 0:
-                raise RuntimeError(result.stderr.decode().strip().split('\n')[-1])
+                raise RuntimeError('Command {!r} failed in {} with RC={}: {}'.format(
+                    cmd,
+                    os.getcwd(),
+                    result.returncode,
+                    result.stderr.decode('utf-8').strip().split('\n')[-1],
+                ))
 
             with output_json.open() as stream:
                 content = json.load(stream)