Fix exception causes all over the codebase

IPython/core/display.py

@@ -987,9 +987,9 b' class Image(DisplayObject):'
         """shortcut for returning metadata with shape information, if defined"""
         try:
             b64_data = b2a_base64(self.data).decode('ascii')
-        except TypeError:
+        except TypeError as e:
             raise FileNotFoundError(
-                "No such file or directory: '%s'" % (self.data))
+                "No such file or directory: '%s'" % (self.data)) from e
         md = {}
         if self.metadata:
             md.update(self.metadata)

IPython/core/page.py

@@ -106,7 +106,7 b' def _detect_screen_size(screen_lines_def):'
         term_flags = termios.tcgetattr(sys.stdout)
     except termios.error as err:
         # can fail on Linux 2.6, pager_page will catch the TypeError
-        raise TypeError('termios error: {0}'.format(err))
+        raise TypeError('termios error: {0}'.format(err)) from err
 
     try:
         scr = curses.initscr()

IPython/core/pylabtools.py

@@ -200,8 +200,8 b' def _reshow_nbagg_figure(fig):'
     """reshow an nbagg figure"""
     try:
         reshow = fig.canvas.manager.reshow
-    except AttributeError:
-        raise NotImplementedError()
+    except AttributeError as e:
+        raise NotImplementedError() from e
     else:
         reshow()
 

IPython/core/tests/test_pylabtools.py

@@ -51,7 +51,7 b' def _check_pil_jpeg_bytes():'
         img.save(buf, 'jpeg')
     except Exception as e:
         ename = e.__class__.__name__
-        raise SkipTest("PIL can't write JPEG to BytesIO: %s: %s" % (ename, e))
+        raise SkipTest("PIL can't write JPEG to BytesIO: %s: %s" % (ename, e)) from e
 
 @dec.skip_without("PIL.Image")
 def test_figure_to_jpeg():

IPython/core/tests/test_run.py

@@ -241,8 +241,8 b' class TestMagicRunSimple(tt.TempFileMixin):'
         if sys.platform == 'win32':
             try:
                 import win32api
-            except ImportError:
-                raise SkipTest("Test requires pywin32")
+            except ImportError as e:
+                raise SkipTest("Test requires pywin32") from e
         src = ("class A(object):\n"
                "    def __del__(self):\n"
                "        print('object A deleted')\n"

IPython/extensions/storemagic.py

@@ -126,13 +126,13 b' class StoreMagics(Magics):'
         if 'd' in opts:
             try:
                 todel = args[0]
-            except IndexError:
-                raise UsageError('You must provide the variable to forget')
+            except IndexError as e:
+                raise UsageError('You must provide the variable to forget') from e
             else:
                 try:
                     del db['autorestore/' + todel]
-                except:
-                    raise UsageError("Can't delete variable '%s'" % todel)
+                except BaseException as e:
+                    raise UsageError("Can't delete variable '%s'" % todel) from e
         # reset
         elif 'z' in opts:
             for k in db.keys('autorestore/*'):
@@ -203,8 +203,8 b' class StoreMagics(Magics):'
                     name = arg
                     try:
                         cmd = ip.alias_manager.retrieve_alias(name)
-                    except ValueError:
-                        raise UsageError("Unknown variable '%s'" % name)
+                    except ValueError as e:
+                        raise UsageError("Unknown variable '%s'" % name) from e
 
                     staliases = db.get('stored_aliases',{})
                     staliases[name] = cmd

IPython/lib/clipboard.py

@@ -16,9 +16,9 b' def win32_clipboard_get():'
     """
     try:
         import win32clipboard
-    except ImportError:
+    except ImportError as e:
         raise TryNext("Getting text from the clipboard requires the pywin32 "
-                      "extensions: http://sourceforge.net/projects/pywin32/")
+                      "extensions: http://sourceforge.net/projects/pywin32/") from e
     win32clipboard.OpenClipboard()
     try:
         text = win32clipboard.GetClipboardData(win32clipboard.CF_UNICODETEXT)
@@ -26,8 +26,8 b' def win32_clipboard_get():'
         try:
             text = win32clipboard.GetClipboardData(win32clipboard.CF_TEXT)
             text = py3compat.cast_unicode(text, py3compat.DEFAULT_ENCODING)
-        except (TypeError, win32clipboard.error):
-            raise ClipboardEmpty
+        except (TypeError, win32clipboard.error) as e:
+            raise ClipboardEmpty from e
     finally:
         win32clipboard.CloseClipboard()
     return text
@@ -52,15 +52,15 b' def tkinter_clipboard_get():'
     """
     try:
         from tkinter import Tk, TclError 
-    except ImportError:
-        raise TryNext("Getting text from the clipboard on this platform requires tkinter.")
+    except ImportError as e:
+        raise TryNext("Getting text from the clipboard on this platform requires tkinter.") from e
         
     root = Tk()
     root.withdraw()
     try:
         text = root.clipboard_get()
-    except TclError:
-        raise ClipboardEmpty
+    except TclError as e:
+        raise ClipboardEmpty from e
     finally:
         root.destroy()
     text = py3compat.cast_unicode(text, py3compat.DEFAULT_ENCODING)

IPython/lib/deepreload.py

@@ -97,21 +97,21 b' def get_parent(globals, level):'
     for x in range(level, 1, -1):
         try:
             dot = name.rindex('.', 0, dot)
-        except ValueError:
+        except ValueError as e:
             raise ValueError("attempted relative import beyond top-level "
-                             "package")
+                             "package") from e
     name = name[:dot]
 
     try:
         parent = sys.modules[name]
-    except:
+    except BaseException as e:
         if orig_level < 1:
             warn("Parent module '%.200s' not found while handling absolute "
                  "import" % name)
             parent = None
         else:
             raise SystemError("Parent module '%.200s' not loaded, cannot "
-                              "perform relative import" % name)
+                              "perform relative import" % name) from e
 
     # We expect, but can't guarantee, if parent != None, that:
     # - parent.__name__ == name
@@ -292,9 +292,9 b' def deep_reload_hook(m):'
     else:
         try:
             parent = sys.modules[name[:dot]]
-        except KeyError:
+        except KeyError as e:
             modules_reloading.clear()
-            raise ImportError("reload(): parent %.200s not in sys.modules" % name[:dot])
+            raise ImportError("reload(): parent %.200s not in sys.modules" % name[:dot]) from e
         subname = name[dot+1:]
         path = getattr(parent, "__path__", None)
 

IPython/lib/display.py

@@ -182,9 +182,9 b' class Audio(DisplayObject):'
 
         try:
             max_abs_value = float(max([abs(x) for x in data]))
-        except TypeError:
+        except TypeError as e:
             raise TypeError('Only lists of mono audio are '
-                'supported if numpy is not installed')
+                'supported if numpy is not installed') from e
 
         normalization_factor = Audio._get_normalization_factor(max_abs_value, normalize)
         scaled = array.array('h', [int(x / normalization_factor * 32767) for x in data])

IPython/lib/inputhook.py

@@ -281,9 +281,9 b' class InputHookManager(object):'
         
         try:
             gui_hook = self.guihooks[gui]
-        except KeyError:
+        except KeyError as e:
             e = "Invalid GUI request {!r}, valid ones are: {}"
-            raise ValueError(e.format(gui, ', '.join(self.guihooks)))
+            raise ValueError(e.format(gui, ', '.join(self.guihooks))) from e
         self._current_gui = gui
 
         app = gui_hook.enable(app)

IPython/lib/inputhookglut.py

@@ -61,10 +61,10 b" if sys.platform == 'darwin':"
             doc='glutCheckLoop(  ) -> None',
             argNames=(),
             )
-    except AttributeError:
+    except AttributeError as e:
         raise RuntimeError(
             '''Your glut implementation does not allow interactive sessions. '''
-            '''Consider installing freeglut.''')
+            '''Consider installing freeglut.''') from e
     glutMainLoopEvent = glutCheckLoop
 elif glut.HAVE_FREEGLUT:
     glutMainLoopEvent = glut.glutMainLoopEvent

IPython/lib/latextools.py

@@ -95,8 +95,8 b" def latex_to_png(s, encode=False, backend=None, wrap=False, color='Black',"
                 try:
                     color = "RGB {}".format(" ".join([str(int(x, 16)) for x in
                                                       textwrap.wrap(color[1:], 2)]))
-                except ValueError:
-                    raise ValueError('Invalid color specification {}.'.format(color))
+                except ValueError as e:
+                    raise ValueError('Invalid color specification {}.'.format(color)) from e
             else:
                 raise ValueError('Invalid color specification {}.'.format(color))
     else:

IPython/paths.py

@@ -113,7 +113,7 b" def locate_profile(profile='default'):"
     from IPython.core.profiledir import ProfileDir, ProfileDirError
     try:
         pd = ProfileDir.find_profile_dir_by_name(get_ipython_dir(), profile)
-    except ProfileDirError:
+    except ProfileDirError as e:
         # IOError makes more sense when people are expecting a path
-        raise IOError("Couldn't find profile %r" % profile)
+        raise IOError("Couldn't find profile %r" % profile) from e
     return pd.location

IPython/sphinxext/custom_doctests.py

@@ -107,10 +107,10 b' def float_doctest(sphinx_shell, args, input_lines, found, submitted):'
         try:
             rtol = float(args[2])
             atol = float(args[3])
-        except IndexError:
+        except IndexError as e:
             e = ("Both `rtol` and `atol` must be specified "
                  "if either are specified: {0}".format(args))
-            raise IndexError(e)
+            raise IndexError(e) from e
 
     try:
         submitted = str_to_array(submitted)

IPython/terminal/magics.py

@@ -181,8 +181,8 b' class TerminalMagics(Magics):'
             else:
                 error('Could not get text from the clipboard.')
             return
-        except ClipboardEmpty:
-            raise UsageError("The clipboard appears to be empty")
+        except ClipboardEmpty as e:
+            raise UsageError("The clipboard appears to be empty") from e
 
         # By default, echo back to terminal unless quiet mode is requested
         if 'q' not in opts:

IPython/terminal/pt_inputhooks/glut.py

@@ -44,10 +44,10 b" if sys.platform == 'darwin':"
             doc='glutCheckLoop(  ) -> None',
             argNames=(),
             )
-    except AttributeError:
+    except AttributeError as e:
         raise RuntimeError(
             '''Your glut implementation does not allow interactive sessions. '''
-            '''Consider installing freeglut.''')
+            '''Consider installing freeglut.''') from e
     glutMainLoopEvent = glutCheckLoop
 elif glut.HAVE_FREEGLUT:
     glutMainLoopEvent = glut.glutMainLoopEvent

IPython/testing/tools.py

@@ -443,8 +443,8 b' def fake_input(inputs):'
     def mock_input(prompt=''):
         try:
             return next(it)
-        except StopIteration:
-            raise EOFError('No more inputs given')
+        except StopIteration as e:
+            raise EOFError('No more inputs given') from e
 
     return patch('builtins.input', mock_input)
 

IPython/utils/_process_win32.py

@@ -75,8 +75,8 b' def _find_cmd(cmd):'
     """Find the full path to a .bat or .exe using the win32api module."""
     try:
         from win32api import SearchPath
-    except ImportError:
-        raise ImportError('you need to have pywin32 installed for this to work')
+    except ImportError as e:
+        raise ImportError('you need to have pywin32 installed for this to work') from e
     else:
         PATH = os.environ['PATH']
         extensions = ['.exe', '.com', '.bat', '.py']

IPython/utils/coloransi.py

@@ -176,9 +176,9 b' class ColorSchemeTable(dict):'
             scheme_test = scheme.lower()
         try:
             scheme_idx = valid_schemes.index(scheme_test)
-        except ValueError:
+        except ValueError as e:
             raise ValueError('Unrecognized color scheme: ' + scheme + \
-                  '\nValid schemes: '+str(scheme_names).replace("'', ",''))
+                  '\nValid schemes: '+str(scheme_names).replace("'', ",'')) from e
         else:
             active = scheme_names[scheme_idx]
             self.active_scheme_name = active

IPython/utils/importstring.py

@@ -31,8 +31,8 b' def import_item(name):'
         module = __import__(package, fromlist=[obj])
         try:
             pak = getattr(module, obj)
-        except AttributeError:
-            raise ImportError('No module named %s' % obj)
+        except AttributeError as e:
+            raise ImportError('No module named %s' % obj) from e
         return pak
     else:
         # called with un-dotted string

IPython/utils/ipstruct.py

@@ -120,7 +120,7 b' class Struct(dict):'
         try:
             self.__setitem__(key, value)
         except KeyError as e:
-            raise AttributeError(e)
+            raise AttributeError(e) from e
 
     def __getattr__(self, key):
         """Get an attr by calling :meth:`dict.__getitem__`.
@@ -145,8 +145,8 b' class Struct(dict):'
         """
         try:
             result = self[key]
-        except KeyError:
-            raise AttributeError(key)
+        except KeyError as e:
+            raise AttributeError(key) from e
         else:
             return result
 

IPython/utils/path.py

@@ -39,8 +39,8 b" if sys.platform == 'win32':"
         """
         try:
             import ctypes
-        except ImportError:
-            raise ImportError('you need to have ctypes installed for this to work')
+        except ImportError as e: 
+            raise ImportError('you need to have ctypes installed for this to work') from e
         _GetLongPathName = ctypes.windll.kernel32.GetLongPathNameW
         _GetLongPathName.argtypes = [ctypes.c_wchar_p, ctypes.c_wchar_p,
             ctypes.c_uint ]

IPython/utils/shimmodule.py

@@ -90,5 +90,5 b' class ShimModule(types.ModuleType):'
         name = "%s.%s" % (self._mirror, key)
         try:
             return import_item(name)
-        except ImportError:
-            raise AttributeError(key)
+        except ImportError as e:
+            raise AttributeError(key) from e

docs/sphinxext/github.py

@@ -40,7 +40,7 b' def make_link_node(rawtext, app, type, slug, options):'
         if not base.endswith('/'):
             base += '/'
     except AttributeError as err:
-        raise ValueError('github_project_url configuration value is not set (%s)' % str(err))
+        raise ValueError('github_project_url configuration value is not set (%s)' % str(err)) from err
 
     ref = base + type + '/' + slug + '/'
     set_classes(options)
@@ -137,7 +137,7 b' def ghcommit_role(name, rawtext, text, lineno, inliner, options={}, content=[]):'
         if not base.endswith('/'):
             base += '/'
     except AttributeError as err:
-        raise ValueError('github_project_url configuration value is not set (%s)' % str(err))
+        raise ValueError('github_project_url configuration value is not set (%s)' % str(err)) from err
 
     ref = base + text
     node = nodes.reference(rawtext, text[:6], refuri=ref, **options)

tools/gh_api.py

@@ -30,8 +30,8 b' class Obj(dict):'
     def __getattr__(self, name):
         try:
             return self[name]
-        except KeyError:
-            raise AttributeError(name)
+        except KeyError as e:
+            raise AttributeError(name) from e
 
     def __setattr__(self, name, val):
         self[name] = val