Fix exception causes all over the codebase

git/__init__.py

@@ -23,8 +23,8 @@ def _init_externals():
 
     try:
         import gitdb
-    except ImportError:
-        raise ImportError("'gitdb' could not be found in your PYTHONPATH")
+    except ImportError as e:
+        raise ImportError("'gitdb' could not be found in your PYTHONPATH") from e
     # END verify import
 
 #} END initialization
@@ -54,7 +54,7 @@ def _init_externals():
         rmtree,
     )
 except GitError as exc:
-    raise ImportError('%s: %s' % (exc.__class__.__name__, exc))
+    raise ImportError('%s: %s' % (exc.__class__.__name__, exc)) from exc
 
 #} END imports
 
@@ -82,5 +82,5 @@ def refresh(path=None):
 try:
     refresh()
 except Exception as exc:
-    raise ImportError('Failed to initialize: {0}'.format(exc))
+    raise ImportError('Failed to initialize: {0}'.format(exc)) from exc
 #################

git/db.py

@@ -53,8 +53,8 @@ def partial_to_complete_sha_hex(self, partial_hexsha):
         try:
             hexsha, _typename, _size = self._git.get_object_header(partial_hexsha)
             return hex_to_bin(hexsha)
-        except (GitCommandError, ValueError):
-            raise BadObject(partial_hexsha)
+        except (GitCommandError, ValueError) as e:
+            raise BadObject(partial_hexsha) from e
         # END handle exceptions
 
     #} END interface

git/index/base.py

@@ -420,9 +420,9 @@ def _write_path_to_stdin(self, proc, filepath, item, fmakeexc, fprogress,
         rval = None
         try:
             proc.stdin.write(("%s\n" % filepath).encode(defenc))
-        except IOError:
+        except IOError as e:
             # pipe broke, usually because some error happened
-            raise fmakeexc()
+            raise fmakeexc() from e
         # END write exception handling
         proc.stdin.flush()
         if read_from_stdout:
@@ -954,7 +954,7 @@ def commit(self, message, parent_commits=None, head=True, author=None,
         if not skip_hooks:
             run_commit_hook('post-commit', self)
         return rval
-    
+
     def _write_commit_editmsg(self, message):
         with open(self._commit_editmsg_filepath(), "wb") as commit_editmsg_file:
             commit_editmsg_file.write(message.encode(defenc))

git/index/fun.py

@@ -82,7 +82,7 @@ def run_commit_hook(name, index, *args):
                                close_fds=is_posix,
                                creationflags=PROC_CREATIONFLAGS,)
     except Exception as ex:
-        raise HookExecutionError(hp, ex)
+        raise HookExecutionError(hp, ex) from ex
     else:
         stdout = []
         stderr = []

git/objects/submodule/base.py

@@ -121,9 +121,9 @@ def _set_cache_(self, attr):
             # default submodule values
             try:
                 self.path = reader.get('path')
-            except cp.NoSectionError:
+            except cp.NoSectionError as e:
                 raise ValueError("This submodule instance does not exist anymore in '%s' file"
-                                 % osp.join(self.repo.working_tree_dir, '.gitmodules'))
+                                 % osp.join(self.repo.working_tree_dir, '.gitmodules')) from e
             # end
             self._url = reader.get('url')
             # git-python extension values - optional
@@ -189,9 +189,9 @@ def _config_parser(cls, repo, parent_commit, read_only):
             assert parent_commit is not None, "need valid parent_commit in bare repositories"
             try:
                 fp_module = cls._sio_modules(parent_commit)
-            except KeyError:
+            except KeyError as e:
                 raise IOError("Could not find %s file in the tree of parent commit %s" %
-                              (cls.k_modules_file, parent_commit))
+                              (cls.k_modules_file, parent_commit)) from e
             # END handle exceptions
         # END handle non-bare working tree
 
@@ -516,9 +516,9 @@ def update(self, recursive=False, init=True, to_latest_revision=False, progress=
                 if not dry_run and osp.isdir(checkout_module_abspath):
                     try:
                         os.rmdir(checkout_module_abspath)
-                    except OSError:
+                    except OSError as e:
                         raise OSError("Module directory at %r does already exist and is non-empty"
-                                      % checkout_module_abspath)
+                                      % checkout_module_abspath) from e
                     # END handle OSError
                 # END handle directory removal
 
@@ -737,8 +737,8 @@ def move(self, module_path, configuration=True, module=True):
                     del(index.entries[ekey])
                     nentry = git.IndexEntry(entry[:3] + (module_checkout_path,) + entry[4:])
                     index.entries[tekey] = nentry
-                except KeyError:
-                    raise InvalidGitRepositoryError("Submodule's entry at %r did not exist" % (self.path))
+                except KeyError as e:
+                    raise InvalidGitRepositoryError("Submodule's entry at %r did not exist" % (self.path)) from e
                 # END handle submodule doesn't exist
 
                 # update configuration
@@ -871,7 +871,7 @@ def remove(self, module=True, force=False, configuration=True, dry_run=False):
                         rmtree(wtd)
                     except Exception as ex:
                         if HIDE_WINDOWS_KNOWN_ERRORS:
-                            raise SkipTest("FIXME: fails with: PermissionError\n  {}".format(ex))
+                            raise SkipTest("FIXME: fails with: PermissionError\n  {}".format(ex)) from ex
                         raise
                 # END delete tree if possible
             # END handle force
@@ -882,7 +882,7 @@ def remove(self, module=True, force=False, configuration=True, dry_run=False):
                     rmtree(git_dir)
                 except Exception as ex:
                     if HIDE_WINDOWS_KNOWN_ERRORS:
-                        raise SkipTest("FIXME: fails with: PermissionError\n  %s", ex)
+                        raise SkipTest("FIXME: fails with: PermissionError\n  %s", ex) from ex
                     else:
                         raise
             # end handle separate bare repository
@@ -1046,8 +1046,8 @@ def module(self):
             if repo != self.repo:
                 return repo
             # END handle repo uninitialized
-        except (InvalidGitRepositoryError, NoSuchPathError):
-            raise InvalidGitRepositoryError("No valid repository at %s" % module_checkout_abspath)
+        except (InvalidGitRepositoryError, NoSuchPathError) as e:
+            raise InvalidGitRepositoryError("No valid repository at %s" % module_checkout_abspath) from e
         else:
             raise InvalidGitRepositoryError("Repository at %r was not yet checked out" % module_checkout_abspath)
         # END handle exceptions

git/objects/tree.py

@@ -203,8 +203,8 @@ def _iter_convert_to_object(self, iterable):
             path = join_path(self.path, name)
             try:
                 yield self._map_id_to_type[mode >> 12](self.repo, binsha, mode, path)
-            except KeyError:
-                raise TypeError("Unknown mode %o found in tree data for path '%s'" % (mode, path))
+            except KeyError as e:
+                raise TypeError("Unknown mode %o found in tree data for path '%s'" % (mode, path)) from e
         # END for each item
 
     def join(self, file):

git/objects/util.py

@@ -203,8 +203,8 @@ def parse_date(string_date):
             # still here ? fail
             raise ValueError("no format matched")
         # END handle format
-    except Exception:
-        raise ValueError("Unsupported date format: %s" % string_date)
+    except Exception as e:
+        raise ValueError("Unsupported date format: %s" % string_date) from e
     # END handle exceptions