How to use the rbtools.clients.errors.SCMError function in RBTools

# installed, and error out if we don't.
        check_gnu_diff()

        property_lines = execute(
            ['cleartool', 'lsview', '-full', '-properties', '-cview'],
            split_lines=True)
        for line in property_lines:
            properties = line.split(' ')
            if properties[0] == 'Properties:':
                # Determine the view type and check if it's supported.
                #
                # Specifically check if webview was listed in properties
                # because webview types also list the 'snapshot'
                # entry in properties.
                if 'webview' in properties:
                    raise SCMError('Webviews are not supported. You can use '
                                   'rbt commands only in dynamic or snapshot '
                                   'views.')
                if 'dynamic' in properties:
                    self.viewtype = 'dynamic'
                else:
                    self.viewtype = 'snapshot'

                break

        # Find current VOB's tag
        vobstag = execute(['cleartool', 'describe', '-short', 'vob:.'],
                          ignore_errors=True).strip()
        if 'Error: ' in vobstag:
            raise SCMError('Failed to generate diff run rbt inside vob.')

        root_path = execute(['cleartool', 'pwv', '-root'],

if not ignore_errors and (rc or has_error):
                for record in result:
                    if 'data' in record:
                        print(record['data'])

                raise SCMError('Failed to execute command: %s\n' % cmd)

            return result

        elif input_string is not None:
            p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
            p.communicate(input_string)  # Send input, wait, set returncode

            if not ignore_errors and p.returncode:
                raise SCMError('Failed to execute command: %s\n' % cmd)

            return None

        else:
            result = execute(cmd, ignore_errors=ignore_errors, *args, **kwargs)

        return result

``diff`` (:py:class:`bytes`):
                The contents of the diff to upload.

            ``base_commit_id` (:py:class:`unicode`, optional):
                The ID of the commit that the change is based on, if available.
                This is necessary for some hosting services that don't provide
                individual file access.
        """
        base = str(revisions['base'])
        tip = str(revisions['tip'])

        if tip == self.REVISION_WORKING_COPY:
            return self._diff_working_copy(base, include_files,
                                           exclude_patterns)
        else:
            raise SCMError('Posting committed changes is not yet supported '
                           'for TFS when using the Team Explorer Everywhere '

if getattr(self.options, 'repository_url', None):
            command.append(self.options.repository_url)

        log = self.svn_log_xml(command)

        if log is not None:
            try:
                root = ElementTree.fromstring(log)
            except ValueError as e:
                # _convert_symbolic_revision() nominally raises a ValueError to
                # indicate any failure to determine the revision number from
                # the log entry.  Here, we explicitly catch a ValueError from
                # ElementTree and raise a generic SCMError so that this
                # specific failure to parse the XML log output is
                # differentiated from the nominal case.
                raise SCMError('Failed to parse svn log - %s.' % e)

            logentry = root.find('logentry')
            if logentry is not None:
                return int(logentry.attrib['revision'])

        raise ValueError

if 'webview' in properties:
                    raise SCMError('Webviews are not supported. You can use '
                                   'rbt commands only in dynamic or snapshot '
                                   'views.')
                if 'dynamic' in properties:
                    self.viewtype = 'dynamic'
                else:
                    self.viewtype = 'snapshot'

                break

        # Find current VOB's tag
        vobstag = execute(['cleartool', 'describe', '-short', 'vob:.'],
                          ignore_errors=True).strip()
        if 'Error: ' in vobstag:
            raise SCMError('Failed to generate diff run rbt inside vob.')

        root_path = execute(['cleartool', 'pwv', '-root'],
                            ignore_errors=True).strip()
        if 'Error: ' in root_path:
            raise SCMError('Failed to generate diff run rbt inside view.')

        # From current working directory cut path to VOB. On Windows
        # and under cygwin, the VOB tag contains the VOB's path including
        # name, e.g. `\new_proj` for a VOB `new_proj` mounted at the root
        # of a drive. On Unix, the VOB tag is similar, but with a different
        # path separator, e.g. `/vobs/new_proj` for our new_proj VOB mounted
        # at `/vobs`.
        cwd = os.getcwd()
        base_path = cwd[:len(root_path) + len(vobstag)]

        return ClearCaseRepositoryInfo(path=base_path,

'base': self.REVISION_BRANCH_BASE,
                    'tip': revisions[0][len(self.REVISION_BRANCH_PREFIX):],
                }
            if revisions[0].startswith(self.REVISION_LABEL_PREFIX):
                return {
                    'base': self.REVISION_LABEL_BASE,
                    'tip': [revisions[0][len(self.REVISION_BRANCH_PREFIX):]],
                }
            # TODO:
            # stream:streamname[@pvob] => review changes in this UCM stream
            #                             (UCM "branch")
            # baseline:baseline[@pvob] => review changes between this baseline
            #                             and the working directory
        elif n_revs == 2:
            if self.viewtype != 'dynamic':
                raise SCMError('To generate a diff using multiple revisions, '
                               'you must use a dynamic view.')

            if (revisions[0].startswith(self.REVISION_LABEL_PREFIX) and
                revisions[1].startswith(self.REVISION_LABEL_PREFIX)):
                return {
                    'base': self.REVISION_LABEL_BASE,
                    'tip': [x[len(self.REVISION_BRANCH_PREFIX):]
                            for x in revisions],
                }
            # TODO:
            # baseline:baseline1[@pvob] baseline:baseline2[@pvob]
            #                             => review changes between these two
            #                                baselines
            pass

        pairs = []

if (tip == SVNClient.REVISION_WORKING_COPY or
            tip.startswith(SVNClient.REVISION_CHANGELIST_PREFIX)):
            return ''

        command = ['-r', '%s:%s' % (base, tip)]

        if getattr(self.options, 'repository_url', None):
            command.append(self.options.repository_url)

        log = self.svn_log_xml(command)

        try:
            root = ElementTree.fromstring(log)
        except ValueError as e:
            raise SCMError('Failed to parse svn log: %s' % e)

        # We skip the first commit message, because we want commit messages
        # corresponding to the changes that will be included in the diff.
        messages = root.findall('.//msg')[1:]

        return '\n\n'.join(message.text for message in messages)

The contents of the diff to upload.

            ``base_commit_id` (:py:class:`unicode`, optional):
                The ID of the commit that the change is based on, if available.
                This is necessary for some hosting services that don't provide
                individual file access.
        """
        base = str(revisions['base'])
        tip = str(revisions['tip'])

        if tip == self.REVISION_WORKING_COPY:
            # TODO: support committed revisions
            return self._diff_working_copy(base, include_files,
                                           exclude_patterns)
        else:
            raise SCMError('Posting committed changes is not yet supported '
                           'for TFS when using the tf.exe wrapper.')

self.viewtype = 'dynamic'
                else:
                    self.viewtype = 'snapshot'

                break

        # Find current VOB's tag
        vobstag = execute(['cleartool', 'describe', '-short', 'vob:.'],
                          ignore_errors=True).strip()
        if 'Error: ' in vobstag:
            raise SCMError('Failed to generate diff run rbt inside vob.')

        root_path = execute(['cleartool', 'pwv', '-root'],
                            ignore_errors=True).strip()
        if 'Error: ' in root_path:
            raise SCMError('Failed to generate diff run rbt inside view.')

        # From current working directory cut path to VOB. On Windows
        # and under cygwin, the VOB tag contains the VOB's path including
        # name, e.g. `\new_proj` for a VOB `new_proj` mounted at the root
        # of a drive. On Unix, the VOB tag is similar, but with a different
        # path separator, e.g. `/vobs/new_proj` for our new_proj VOB mounted
        # at `/vobs`.
        cwd = os.getcwd()
        base_path = cwd[:len(root_path) + len(vobstag)]

        return ClearCaseRepositoryInfo(path=base_path,
                                       base_path=base_path,
                                       vobstag=vobstag)