More user-friendly exceptions

pymake/__init__.py

@@ -1,7 +1,7 @@
 from ._main import main
 from ._version import __version__  # NOQA
 from ._pymake import __author__, \
-    PymakeTypeError, PymakeKeyError
+    PymakeTypeError, PymakeKeyError, CmdExecutionError
 
 __all__ = ['main', '__version__', '__author__',
-           'PymakeTypeError', 'PymakeKeyError']
+           'PymakeTypeError', 'PymakeKeyError', 'CmdExecutionError']

pymake/_pymake.py

@@ -3,7 +3,7 @@
 """
 from __future__ import absolute_import
 # import compatibility functions and utilities
-from ._utils import ConfigParser, StringIO, shlex
+from ._utils import ConfigParser, StringIO, shlex, raise_from
 import io
 import re
 from subprocess import check_call
@@ -109,6 +109,24 @@ def parse_makefile_aliases(filepath):
     return commands, default_alias
 
 
+class CmdExecutionError(Exception):
+    """
+    Exception raised when a command execution returned an error.
+
+    The python __cause__ is hidden,
+    and only the command and final message is displayed.
+    """
+    __slots__ = 'cause', 'parsed_cmd'
+
+    def __init__(self, parsed_cmd, cause):
+        super(CmdExecutionError, self).__init__()
+        self.cause = cause
+        self.parsed_cmd = parsed_cmd
+
+    def __str__(self):
+        return "Error executing CMD '%s': %s" % (self.parsed_cmd, self.cause)
+
+
 def execute_makefile_commands(
         commands, alias, silent=False, just_print=False, ignore_errors=False):
     """
@@ -141,6 +159,7 @@ def execute_makefile_commands(
             # Launch the command and wait to finish (synchronized call)
             try:
                 check_call(parsed_cmd)
-            except:
+            except Exception as e:
                 if not ignore_errors:
-                    raise
+                    raise_from(CmdExecutionError(' '.join(parsed_cmd), e),
+                               None)

pymake/_utils.py

@@ -20,6 +20,29 @@
     except NameError:
         _unicode = str
 
+    try:
+        from six import raise_from
+    except ImportError:
+        if sys.version_info[:2] == (3, 2):
+            exec("""def raise_from(value, from_value):
+            try:
+                if from_value is None:
+                    raise value
+                raise value from from_value
+            finally:
+                value = None
+        """)
+        elif sys.version_info[:2] > (3, 2):
+            exec("""def raise_from(value, from_value):
+            try:
+                raise value from from_value
+            finally:
+                value = None
+        """)
+        else:
+            def raise_from(value, from_value):
+                raise value
+
 if sys.version_info >= (2, 7):  # pragma: no cover
     import shlex
 else:  # pragma: no cover

pymake/tests/tests_main.py

@@ -1,7 +1,7 @@
 import sys
 import subprocess
 from os import path
-from pymake import main, PymakeKeyError, PymakeTypeError
+from pymake import main, PymakeKeyError, PymakeTypeError, CmdExecutionError
 
 dn = path.dirname
 fname = path.join(dn(dn(dn(path.abspath(__file__)))),
@@ -64,8 +64,8 @@ def test_ignore_errors():
     """Test --ignore-errors"""
     try:
         main(['-s', '-f', fname, 'err'])
-    except OSError:
-        pass  # test passed if file not found
+    except CmdExecutionError as e:
+        assert "Error executing CMD" in str(e)  # test passed if file not found
     else:
         raise PymakeTypeError('err')