Fix issue 4161 (#6919)

* Fix issue 4161

* Minor tweaks

* Fix log title

i18n/en.json

@@ -1989,127 +1989,127 @@
   },
   {
     "id": "api.slackimport.slack_add_bot_user.email_pwd",
-    "translation": "Slack Bot/Integration Posts Import User: Email, Password: {{.Email}}, {{.Password}}\r\n"
+    "translation": "The Integration/Slack Bot user with email {{.Email}} and password {{.Password}} has been imported.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_bot_user.unable_import",
-    "translation": "Unable to import Slack Bot/Integration Posts Import User: {{.Username}}\r\n"
+    "translation": "Unable to import the Integration/Slack Bot user {{.Username}}.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_channels.added",
-    "translation": "\r\n Channels Added \r\n"
+    "translation": "\r\nChannels added:\r\n"
   },
   {
     "id": "api.slackimport.slack_add_channels.failed_to_add_user",
-    "translation": "Failed to add user to channel: {{.Username}}\r\n"
+    "translation": "Unable to add Slack user {{.Username}} to channel.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_channels.import_failed",
-    "translation": "Failed to import: {{.DisplayName}}\r\n"
+    "translation": "Unable to import Slack channel {{.DisplayName}}.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_channels.import_failed.warn",
-    "translation": "Slack Importer: Failed to import channel: %s"
+    "translation": "Slack Import: Unable to import Slack channel: %s."
   },
   {
     "id": "api.slackimport.slack_add_channels.merge",
-    "translation": "Merged with existing channel: {{.DisplayName}}\r\n"
+    "translation": "The Slack channel {{.DisplayName}} already exists as an active Mattermost channel. Both channels have been merged.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_posts.attach_files.error",
-    "translation": "Encountered error attaching files to post, post_id=%s, file_ids=%v, err=%v"
+    "translation": "Slack Import: An error occurred when attaching files to a message, post_id=%s, file_ids=%v, err=%v."
   },
   {
     "id": "api.slackimport.slack_add_posts.bot.warn",
-    "translation": "Slack bot posts are not imported yet"
+    "translation": "Slack Import: Slack bot messages cannot be imported yet."
   },
   {
     "id": "api.slackimport.slack_add_posts.bot_user_no_exists.warn",
-    "translation": "Slack Importer: Not importing bot message as the bot-importing user does not exist."
+    "translation": "Slack Import: Unable to import the bot message as the bot user does not exist."
   },
   {
     "id": "api.slackimport.slack_add_posts.msg_no_comment.debug",
-    "translation": "File comment undefined"
+    "translation": "Slack Import: Unable to import the message as it has no comments."
   },
   {
     "id": "api.slackimport.slack_add_posts.msg_no_usr.debug",
-    "translation": "Message without user"
+    "translation": "Slack Import: Unable to import the message as the user field is missing."
   },
   {
     "id": "api.slackimport.slack_add_posts.no_bot_id.warn",
-    "translation": "Slack Importer: Not importing bot message due to lack of BotId field."
+    "translation": "Slack Import: Unable to import bot message as the BotId field is missing."
   },
   {
     "id": "api.slackimport.slack_add_posts.unsupported.warn",
-    "translation": "Unsupported post type: %v, %v"
+    "translation": "Slack Import: Unable to import the message as its type is not supported: post_type=%v, post_subtype=%v."
   },
   {
     "id": "api.slackimport.slack_add_posts.upload_file_not_found.warn",
-    "translation": "No file found in Slack export for file upload message with file ID {{.FileId}}"
+    "translation": "Slack Import: Unable to import file {{.FileId}} as the file is missing from the Slack export zip file."
   },
   {
     "id": "api.slackimport.slack_add_posts.upload_file_not_in_json.warn",
-    "translation": "Cannot import file for upload post with no \"file\" section present in export."
+    "translation": "Slack Import: Unable to attach the file to the post as the latter has no \"file\" section present in Slack export."
   },
   {
     "id": "api.slackimport.slack_add_posts.upload_file_open_failed.warn",
-    "translation": "Could not open the upload file with ID {{.FileId}} in the export archive with error: {{.Error}}"
+    "translation": "Slack Import: Unable to open the file {{.FileId}} from the Slack export: {{.Error}}."
   },
   {
     "id": "api.slackimport.slack_add_posts.upload_file_upload_failed.warn",
-    "translation": "Uploading the file for upload message with file ID {{.FileId}} failed with error: {{.Error}}"
+    "translation": "Slack Import: An error occurred when uploading file {{.FileId}}: {{.Error}}."
   },
   {
     "id": "api.slackimport.slack_add_posts.user_no_exists.debug",
-    "translation": "User: %v does not exist!"
+    "translation": "Slack Import: Unable to add the message as the Slack user %v does not exist in Mattermost."
   },
   {
     "id": "api.slackimport.slack_add_posts.without_user.debug",
-    "translation": "Message without user"
+    "translation": "Slack Import: Unable to import the message as the user field is missing."
   },
   {
     "id": "api.slackimport.slack_add_users.created",
-    "translation": "\r\n Users Created\r\n"
+    "translation": "\r\nUsers created:\r\n"
   },
   {
     "id": "api.slackimport.slack_add_users.email_pwd",
-    "translation": "Email, Password: {{.Email}}, {{.Password}}\r\n"
+    "translation": "Slack user with email {{.Email}} and password {{.Password}} has been imported.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_users.merge_existing",
-    "translation": "Merged user with existing account: {{.Email}}, {{.Username}}\r\n"
+    "translation": "Slack user merged with an existing Mattermost user with matching email {{.Email}} and username {{.Username}}.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_users.merge_existing_failed",
-    "translation": "Tried to merge user with existing account: {{.Email}}, {{.Username}}, but failed to add the user to this team.\r\n"
+    "translation": "Slack user merged with an existing Mattermost user with matching email {{.Email}} and username {{.Username}}, but was unable to add the user to their team.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_users.missing_email_address",
-    "translation": "User {{.Username}} does not have an email address in the Slack export. Using {{.Email}} as a placeholder. The user should update their email address once logged in to the system.\r\n"
+    "translation": "User {{.Username}} does not have an email address in the Slack export. Used {{.Email}} as a placeholder. The user should update their email address once logged in to the system.\r\n"
   },
   {
     "id": "api.slackimport.slack_add_users.missing_email_address.warn",
-    "translation": "User {{.Username}} does not have an email address in the Slack export. Using {{.Email}} as a placeholder. The user should update their email address once logged in to the system."
+    "translation": "Slack Import: User {{.Username}} does not have an email address in the Slack export. Used {{.Email}} as a placeholder. The user should update their email address once logged in to the system."
   },
   {
     "id": "api.slackimport.slack_add_users.unable_import",
-    "translation": "Unable to import user: {{.Username}}\r\n"
+    "translation": "Unable to import Slack user: {{.Username}}.\r\n"
   },
   {
     "id": "api.slackimport.slack_convert_channel_mentions.compile_regexp_failed.warn",
-    "translation": "Failed to compile the !channel matching regular expression for Slack channel {{.ChannelID}} {{.ChannelName}}"
+    "translation": "Slack Import: Unable to compile the !channel, matching regular expression for the Slack channel {{.ChannelName}} (id={{.ChannelID}})."
   },
   {
     "id": "api.slackimport.slack_convert_timestamp.bad.warn",
-    "translation": "Bad timestamp detected"
+    "translation": "Slack Import: Bad timestamp detected."
   },
   {
     "id": "api.slackimport.slack_convert_user_mentions.compile_regexp_failed.warn",
-    "translation": "Failed to compile the @mention matching regular expression for Slack user {{.UserID}} {{.Username}}"
+    "translation": "Slack Import: Unable to compile the @mention, matching regular expression for the Slack user {{.Username}} (id={{.UserID}})."
   },
   {
     "id": "api.slackimport.slack_deactivate_bot_user.failed_to_deactivate",
-    "translation": "Slack Importer: Failed to deactivate the bot-importing user."
+    "translation": "Slack Import: Unable to deactivate the user account used for the bot."
   },
   {
     "id": "api.slackimport.slack_import.log",
@@ -2117,11 +2117,11 @@
   },
   {
     "id": "api.slackimport.slack_import.note1",
-    "translation": "- Some posts may not have been imported because they where not supported by this importer.\r\n"
+    "translation": "- Some messages may not have been imported because they were not supported by this importer.\r\n"
   },
   {
     "id": "api.slackimport.slack_import.note2",
-    "translation": "- Slack bot posts are currently not supported.\r\n"
+    "translation": "- Slack bot messages are currently not supported.\r\n"
   },
   {
     "id": "api.slackimport.slack_import.note3",
@@ -2129,43 +2129,43 @@
   },
   {
     "id": "api.slackimport.slack_import.notes",
-    "translation": "\r\n Notes \r\n"
+    "translation": "\r\nNotes:\r\n"
   },
   {
     "id": "api.slackimport.slack_import.open.app_error",
-    "translation": "Unable to open: {{.Filename}}"
+    "translation": "Unable to open the file: {{.Filename}}.\r\n"
   },
   {
     "id": "api.slackimport.slack_import.team_fail",
-    "translation": "Failed to get team to import into.\r\n"
+    "translation": "Unable to get the team to import into.\r\n"
   },
   {
     "id": "api.slackimport.slack_import.zip.app_error",
-    "translation": "Unable to open zip file"
+    "translation": "Unable to open the Slack export zip file.\r\n"
   },
   {
     "id": "api.slackimport.slack_parse_channels.error",
-    "translation": "Error parsing slack channels. Import may work anyway."
+    "translation": "Slack Import: Error occurred when parsing some Slack channels. Import may work anyway."
   },
   {
     "id": "api.slackimport.slack_parse_posts.error",
-    "translation": "Error parsing some slack posts. Import may work anyway."
+    "translation": "Slack Import: Error occurred when parsing some Slack posts. Import may work anyway."
   },
   {
     "id": "api.slackimport.slack_sanitise_channel_properties.display_name_too_long.warn",
-    "translation": "Slack Importer: Channel {{.ChannelName}} has a display name which is too long. It will be truncated when imported."
+    "translation": "Slack Import: Channel {{.ChannelName}} display name exceeds the maximum length. It will be truncated when imported."
   },
   {
     "id": "api.slackimport.slack_sanitise_channel_properties.header_too_long.warn",
-    "translation": "Slack Importer: Channel {{.ChannelName}} has a header which is too long. It will be truncated when imported."
+    "translation": "Slack Import: Channel {{.ChannelName}} header exceeds the maximum length. It will be truncated when imported."
   },
   {
     "id": "api.slackimport.slack_sanitise_channel_properties.name_too_long.warn",
-    "translation": "Slack Importer: Channel {{.ChannelName}} has a name which is too long. It will be truncated when imported."
+    "translation": "Slack Import: Channel {{.ChannelName}} handle exceeds the maximum length. It will be truncated when imported."
   },
   {
     "id": "api.slackimport.slack_sanitise_channel_properties.purpose_too_long.warn",
-    "translation": "Slack Importer: Channel {{.ChannelName}} has a purpose which is too long. It will be truncated when imported."
+    "translation": "Slack Import: Channel {{.ChannelName}} purpose exceeds the maximum length. It will be truncated when imported."
   },
   {
     "id": "api.status.init.debug",