cleanup: Update codebase to expect Python 3.6

- Bump minimum version to Python 3.6.
- Use f-strings in a lot of places.

Change-Id: I2aa70197230fcec2eff8e7c8eb754f20c08075bb
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/389034
Tested-by: Jason R. Coombs <jaraco@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Jason R. Coombs <jaraco@google.com>

manifest_xml.py

@@ -114,9 +114,7 @@ def XmlInt(node, attr, default=None):
     try:
         return int(value)
     except ValueError:
-        raise ManifestParseError(
-            'manifest: invalid %s="%s" integer' % (attr, value)
-        )
+        raise ManifestParseError(f'manifest: invalid {attr}="{value}" integer')
 
 
 class _Default:
@@ -810,7 +808,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                         ret.setdefault(child.nodeName, []).append(element)
                     else:
                         raise ManifestParseError(
-                            'Unhandled element "%s"' % (child.nodeName,)
+                            f'Unhandled element "{child.nodeName}"'
                         )
 
                     append_children(element, child)
@@ -1258,12 +1256,10 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         try:
             root = xml.dom.minidom.parse(path)
         except (OSError, xml.parsers.expat.ExpatError) as e:
-            raise ManifestParseError(
-                "error parsing manifest %s: %s" % (path, e)
-            )
+            raise ManifestParseError(f"error parsing manifest {path}: {e}")
 
         if not root or not root.childNodes:
-            raise ManifestParseError("no root node in %s" % (path,))
+            raise ManifestParseError(f"no root node in {path}")
 
         for manifest in root.childNodes:
             if (
@@ -1272,7 +1268,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
             ):
                 break
         else:
-            raise ManifestParseError("no <manifest> in %s" % (path,))
+            raise ManifestParseError(f"no <manifest> in {path}")
 
         nodes = []
         for node in manifest.childNodes:
@@ -1282,7 +1278,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     msg = self._CheckLocalPath(name)
                     if msg:
                         raise ManifestInvalidPathError(
-                            '<include> invalid "name": %s: %s' % (name, msg)
+                            f'<include> invalid "name": {name}: {msg}'
                         )
                 include_groups = ""
                 if parent_groups:
@@ -1314,7 +1310,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     raise
                 except Exception as e:
                     raise ManifestParseError(
-                        "failed parsing included manifest %s: %s" % (name, e)
+                        f"failed parsing included manifest {name}: {e}"
                     )
             else:
                 if parent_groups and node.nodeName == "project":
@@ -1765,13 +1761,13 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                 msg = self._CheckLocalPath(name)
                 if msg:
                     raise ManifestInvalidPathError(
-                        '<submanifest> invalid "name": %s: %s' % (name, msg)
+                        f'<submanifest> invalid "name": {name}: {msg}'
                     )
         else:
             msg = self._CheckLocalPath(path)
             if msg:
                 raise ManifestInvalidPathError(
-                    '<submanifest> invalid "path": %s: %s' % (path, msg)
+                    f'<submanifest> invalid "path": {path}: {msg}'
                 )
 
         submanifest = _XmlSubmanifest(
@@ -1806,7 +1802,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         msg = self._CheckLocalPath(name, dir_ok=True)
         if msg:
             raise ManifestInvalidPathError(
-                '<project> invalid "name": %s: %s' % (name, msg)
+                f'<project> invalid "name": {name}: {msg}'
             )
         if parent:
             name = self._JoinName(parent.name, name)
@@ -1816,7 +1812,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
             remote = self._default.remote
         if remote is None:
             raise ManifestParseError(
-                "no remote for project %s within %s" % (name, self.manifestFile)
+                f"no remote for project {name} within {self.manifestFile}"
             )
 
         revisionExpr = node.getAttribute("revision") or remote.revision
@@ -1837,7 +1833,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
             msg = self._CheckLocalPath(path, dir_ok=True, cwd_dot_ok=True)
             if msg:
                 raise ManifestInvalidPathError(
-                    '<project> invalid "path": %s: %s' % (path, msg)
+                    f'<project> invalid "path": {path}: {msg}'
                 )
 
         rebase = XmlBool(node, "rebase", True)
@@ -2094,7 +2090,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         if not cwd_dot_ok or parts != ["."]:
             for part in set(parts):
                 if part in {".", "..", ".git"} or part.startswith(".repo"):
-                    return "bad component: %s" % (part,)
+                    return f"bad component: {part}"
 
         if not dir_ok and resep.match(path[-1]):
             return "dirs not allowed"
@@ -2130,7 +2126,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         msg = cls._CheckLocalPath(dest)
         if msg:
             raise ManifestInvalidPathError(
-                '<%s> invalid "dest": %s: %s' % (element, dest, msg)
+                f'<{element}> invalid "dest": {dest}: {msg}'
             )
 
         # |src| is the file we read from or path we point to for symlinks.
@@ -2141,7 +2137,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         )
         if msg:
             raise ManifestInvalidPathError(
-                '<%s> invalid "src": %s: %s' % (element, src, msg)
+                f'<{element}> invalid "src": {src}: {msg}'
             )
 
     def _ParseCopyFile(self, project, node):
@@ -2185,7 +2181,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         v = self._remotes.get(name)
         if not v:
             raise ManifestParseError(
-                "remote %s not defined in %s" % (name, self.manifestFile)
+                f"remote {name} not defined in {self.manifestFile}"
             )
         return v