updatecheck: support XDG-based token location

Have updatecheck look in $XDG_DATA_HOME/zcash/updatecheck/token for the GH
token. Having one in the repo will still take precedence (for pre-existing
users, as well as if you want to override the token used in a particular
case). The new location is standardized, exists at the user level (as the token
logically does), and means that you don't need to copy files around if you get a
new clone or worktree to do a release.

doc/release-process.md

@@ -28,9 +28,9 @@ Check that dependencies are up-to-date or have been postponed:
 $ ./qa/zcash/updatecheck.py
 ```
 
-You can optionally create an `.updatecheck-token` file in the root of the
-repository to avoid running into GitHub rate limiting. Create an unprivileged
-personal access token on GitHub and copy the value into the file.
+You can optionally create an `$XDG_DATA_HOME/zcash/updatecheck/token` file to
+avoid running into GitHub rate limiting. Create an unprivileged personal access
+token on GitHub and copy the value into the file.
 
 If there are updates that have not been postponed, review their changelogs
 for urgent security fixes, and if there aren't any, postpone the update by
@@ -58,9 +58,8 @@ The release script has the following dependencies:
 
 - `help2man`
 - `debchange` (part of the devscripts Debian package)
-
-You can optionally install the `progressbar2` Python module with pip to have a
-progress bar displayed during the build process.
+- the python modules `progressbar2` (optional - displays a progress bar),
+  `requests` and `xdg`
 
 ## Versioning
 

qa/zcash/updatecheck.py

@@ -35,6 +35,7 @@ import requests
 import os
 import re
 import sys
+import xdg
 import datetime
 
 SOURCE_ROOT = os.path.join(os.path.dirname(os.path.realpath(__file__)), "..", "..")
@@ -113,6 +114,8 @@ def get_dependency_list():
 
 def parse_token():
     token_path = os.path.realpath(os.path.join(SOURCE_ROOT, ".updatecheck-token"))
+    if not os.path.exists(token_path):
+        token_path = os.path.join(xdg.xdg_data_home(), "zcash/updatecheck/token")
     try:
         with open(token_path, encoding='utf8') as f:
             token = f.read().strip()