Get rid of Python 3.7 dependency

sphinx_multiversion/git.py

@@ -18,7 +18,7 @@ GitRef = collections.namedtuple('VersionRef', [
 
 def get_all_refs(gitroot):
     cmd = ("git", "for-each-ref", "--format",
-           "%(objectname)\t%(refname)\t%(creatordate:iso-strict)", "refs")
+           "%(objectname)\t%(refname)\t%(creatordate:iso)", "refs")
     output = subprocess.check_output(cmd, cwd=gitroot).decode()
     for line in output.splitlines():
         is_remote = False
@@ -28,7 +28,7 @@ def get_all_refs(gitroot):
 
         commit = fields[0]
         refname = fields[1]
-        creatordate = datetime.datetime.fromisoformat(fields[2])
+        creatordate = datetime.datetime.strptime(fields[2], "%Y-%m-%d %H:%M:%S %z")
 
         # Parse refname
         matchobj = re.match(r"^refs/(heads|tags|remotes/[^/]+)/(\S+)$", refname)

sphinx_multiversion/main.py

@@ -127,7 +127,7 @@ def main(argv=None):
                 "is_released": bool(
                     re.match(config.smv_released_pattern, gitref.refname)),
                 "source": gitref.source,
-                "creatordate": gitref.creatordate.isoformat(),
+                "creatordate": gitref.creatordate.strftime("%Y-%m-%d %H:%M:%S %z"),
                 "sourcedir": current_sourcedir,
                 "outputdir": outputdir,
                 "docnames": list(project.discover())

sphinx_multiversion/sphinx.py

@@ -151,7 +151,7 @@ def config_inited(app, config):
     if not config.today:
         config.today = sphinx_i18n.format_date(
             format=config.today_fmt or _('%b %d, %Y'),
-            date=datetime.datetime.fromisoformat(data["creatordate"]),
+            date=datetime.datetime.strftime(data["creatordate"], "%Y-%m-%d %H:%M:%S %z"),
             language=config.language)