diff --git a/rhodecode/api/__init__.py b/rhodecode/api/__init__.py
--- a/rhodecode/api/__init__.py
+++ b/rhodecode/api/__init__.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/exc.py b/rhodecode/api/exc.py
--- a/rhodecode/api/exc.py
+++ b/rhodecode/api/exc.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/__init__.py b/rhodecode/api/tests/__init__.py
--- a/rhodecode/api/tests/__init__.py
+++ b/rhodecode/api/tests/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/conftest.py b/rhodecode/api/tests/conftest.py
--- a/rhodecode/api/tests/conftest.py
+++ b/rhodecode/api/tests/conftest.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_add_field_to_repo.py b/rhodecode/api/tests/test_add_field_to_repo.py
--- a/rhodecode/api/tests/test_add_field_to_repo.py
+++ b/rhodecode/api/tests/test_add_field_to_repo.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_add_user_to_user_group.py b/rhodecode/api/tests/test_add_user_to_user_group.py
--- a/rhodecode/api/tests/test_add_user_to_user_group.py
+++ b/rhodecode/api/tests/test_add_user_to_user_group.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_api.py b/rhodecode/api/tests/test_api.py
--- a/rhodecode/api/tests/test_api.py
+++ b/rhodecode/api/tests/test_api.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_cleanup_sessions.py b/rhodecode/api/tests/test_cleanup_sessions.py
--- a/rhodecode/api/tests/test_cleanup_sessions.py
+++ b/rhodecode/api/tests/test_cleanup_sessions.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2017-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_close_pull_request.py b/rhodecode/api/tests/test_close_pull_request.py
--- a/rhodecode/api/tests/test_close_pull_request.py
+++ b/rhodecode/api/tests/test_close_pull_request.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/tests/test_comment_commit.py b/rhodecode/api/tests/test_comment_commit.py
--- a/rhodecode/api/tests/test_comment_commit.py
+++ b/rhodecode/api/tests/test_comment_commit.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/utils.py b/rhodecode/api/utils.py
--- a/rhodecode/api/utils.py
+++ b/rhodecode/api/utils.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2014-2020 RhodeCode GmbH
 #
@@ -28,7 +28,7 @@ import logging
 from rhodecode.api.exc import JSONRPCError
 from rhodecode.lib.auth import (
     HasPermissionAnyApi, HasRepoPermissionAnyApi, HasRepoGroupPermissionAnyApi)
-from rhodecode.lib.utils import safe_unicode
+from rhodecode.lib.str_utils import safe_str
 from rhodecode.lib.vcs.exceptions import RepositoryError
 from rhodecode.lib.view_utils import get_commit_from_ref_name
 from rhodecode.lib.utils2 import str2bool
@@ -368,7 +368,7 @@ def build_commit_data(rhodecode_vcs_repo
         from rhodecode.lib import diffs
 
         _diff = rhodecode_vcs_repo.get_diff(commit1, commit2,)
-        diff_processor = diffs.DiffProcessor(_diff, format='newdiff', show_full_diff=True)
+        diff_processor = diffs.DiffProcessor(_diff, diff_format='newdiff', show_full_diff=True)
 
         for dp in diff_processor.prepare():
             del dp['stats']['ops']
@@ -446,7 +446,7 @@ def _get_commit_dict(
             "deleted": None
         }
     return {
-        "filename": safe_unicode(filename),
+        "filename": safe_str(filename),
         "op": op,
 
         # extra details
diff --git a/rhodecode/api/views/__init__.py b/rhodecode/api/views/__init__.py
--- a/rhodecode/api/views/__init__.py
+++ b/rhodecode/api/views/__init__.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2015-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/views/deprecated_api.py b/rhodecode/api/views/deprecated_api.py
--- a/rhodecode/api/views/deprecated_api.py
+++ b/rhodecode/api/views/deprecated_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/views/gist_api.py b/rhodecode/api/views/gist_api.py
--- a/rhodecode/api/views/gist_api.py
+++ b/rhodecode/api/views/gist_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
@@ -48,14 +48,16 @@ def get_gist(request, apiuser, gistid, c
 
     gist = get_gist_or_error(gistid)
     content = Optional.extract(content)
+
     if not has_superadmin_permission(apiuser):
         if gist.gist_owner != apiuser.user_id:
             raise JSONRPCError('gist `%s` does not exist' % (gistid,))
     data = gist.get_api_data()
+
     if content:
         from rhodecode.model.gist import GistModel
         rev, gist_files = GistModel().get_gist_files(gistid)
-        data['content'] = dict([(x.path, x.content) for x in gist_files])
+        data['content'] = dict([(x.path, x.str_content) for x in gist_files])
     return data
 
 
diff --git a/rhodecode/api/views/pull_request_api.py b/rhodecode/api/views/pull_request_api.py
--- a/rhodecode/api/views/pull_request_api.py
+++ b/rhodecode/api/views/pull_request_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
@@ -525,9 +525,7 @@ def comment_pull_request(
             raise JSONRPCError('userid is not the same as your user')
 
     if pull_request.is_closed():
-        raise JSONRPCError(
-            'pull request `%s` comment failed, pull request is closed' % (
-                pullrequestid,))
+        raise JSONRPCError(f'pull request `{pullrequestid}` comment failed, pull request is closed')
 
     if not PullRequestModel().check_user_read(
             pull_request, apiuser, api=True):
@@ -545,34 +543,29 @@ def comment_pull_request(
             'Both message and status parameters are missing. '
             'At least one is required.')
 
-    if (status not in (st[0] for st in ChangesetStatus.STATUSES) and
-            status is not None):
-        raise JSONRPCError('Unknown comment status: `%s`' % status)
+    if status and status not in (st[0] for st in ChangesetStatus.STATUSES):
+        raise JSONRPCError(f'Unknown comment status: `{status}`')
 
     if commit_id and commit_id not in pull_request.revisions:
-        raise JSONRPCError(
-            'Invalid commit_id `%s` for this pull request.' % commit_id)
+        raise JSONRPCError(f'Invalid commit_id `{commit_id}` for this pull request.')
 
     allowed_to_change_status = PullRequestModel().check_user_change_status(
         pull_request, apiuser)
 
     # if commit_id is passed re-validated if user is allowed to change status
-    # based on latest commit_id from the PR
+    # based on the latest commit_id from the PR
     if commit_id:
         commit_idx = pull_request.revisions.index(commit_id)
         if commit_idx != 0:
+            log.warning('Resetting allowed_to_change_status = False because commit is NOT the latest in pull-request')
             allowed_to_change_status = False
 
     if resolves_comment_id:
         comment = ChangesetComment.get(resolves_comment_id)
         if not comment:
-            raise JSONRPCError(
-                'Invalid resolves_comment_id `%s` for this pull request.'
-                % resolves_comment_id)
+            raise JSONRPCError(f'Invalid resolves_comment_id `{resolves_comment_id}` for this pull request.')
         if comment.comment_type != ChangesetComment.COMMENT_TYPE_TODO:
-            raise JSONRPCError(
-                'Comment `%s` is wrong type for setting status to resolved.'
-                % resolves_comment_id)
+            raise JSONRPCError(f'Comment `{resolves_comment_id}` is wrong type for setting status to resolved.')
 
     text = message
     status_label = ChangesetStatus.get_status_lbl(status)
@@ -602,6 +595,7 @@ def comment_pull_request(
         extra_recipients=extra_recipients,
         send_email=send_email
     )
+
     is_inline = comment.is_inline
 
     if allowed_to_change_status and status:
@@ -648,6 +642,7 @@ def comment_pull_request(
 
     return data
 
+
 def _reviewers_validation(obj_list):
     schema = ReviewerListSchema()
     try:
diff --git a/rhodecode/api/views/repo_api.py b/rhodecode/api/views/repo_api.py
--- a/rhodecode/api/views/repo_api.py
+++ b/rhodecode/api/views/repo_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
@@ -36,7 +36,7 @@ from rhodecode.lib.auth import (
     HasRepoPermissionAnyApi)
 from rhodecode.lib.celerylib.utils import get_task_id
 from rhodecode.lib.utils2 import (
-    str2bool, time_to_datetime, safe_str, safe_int, safe_unicode)
+    str2bool, time_to_datetime, safe_str, safe_int)
 from rhodecode.lib.ext_json import json
 from rhodecode.lib.exceptions import (
     StatusChangeOnClosedPullRequestError, CommentVersionMismatch)
@@ -204,6 +204,7 @@ def get_repo(request, apiuser, repoid, c
     data = repo.get_api_data(include_secrets=include_secrets)
     data['permissions'] = permissions
     data['followers'] = following_users
+
     return data
 
 
@@ -474,7 +475,9 @@ def get_repo_nodes(request, apiuser, rep
 
     _extended_types = ['basic', 'full']
     if details not in _extended_types:
-        raise JSONRPCError('ret_type must be one of %s' % (','.join(_extended_types)))
+        ret_types = ','.join(_extended_types)
+        raise JSONRPCError(f'ret_type must be one of {ret_types}')
+
     extended_info = False
     content = False
     if details == 'basic':
@@ -500,20 +503,19 @@ def get_repo_nodes(request, apiuser, rep
             'files': _f,
             'dirs': _d,
         }
+
         return _map[ret_type]
     except KeyError:
-        raise JSONRPCError(
-            'ret_type must be one of %s' % (','.join(sorted(_map.keys()))))
+        keys = ','.join(sorted(_map.keys()))
+        raise JSONRPCError(f'ret_type must be one of {keys}')
     except Exception:
         log.exception("Exception occurred while trying to get repo nodes")
-        raise JSONRPCError(
-            'failed to get repo: `%s` nodes' % repo.repo_name
-        )
+        raise JSONRPCError(f'failed to get repo: `{repo.repo_name}` nodes')
 
 
 @jsonrpc_method()
 def get_repo_file(request, apiuser, repoid, commit_id, file_path,
-                  max_file_bytes=Optional(None), details=Optional('basic'),
+                  max_file_bytes=Optional(0), details=Optional('basic'),
                   cache=Optional(True)):
     """
     Returns a single file from repository at given revision.
@@ -564,10 +566,12 @@ def get_repo_file(request, apiuser, repo
 
     cache = Optional.extract(cache, binary=True)
     details = Optional.extract(details)
+    max_file_bytes = Optional.extract(max_file_bytes)
+
     _extended_types = ['minimal', 'minimal+search', 'basic', 'full']
     if details not in _extended_types:
-        raise JSONRPCError(
-            'ret_type must be one of %s, got %s' % (','.join(_extended_types)), details)
+        ret_types = ','.join(_extended_types)
+        raise JSONRPCError(f'ret_type must be one of %s, got {ret_types}', details)
     extended_info = False
     content = False
 
@@ -580,7 +584,7 @@ def get_repo_file(request, apiuser, repo
     elif details == 'full':
         extended_info = content = True
 
-    file_path = safe_unicode(file_path)
+    file_path = safe_str(file_path)
     try:
         # check if repo is not empty by any chance, skip quicker if it is.
         _scm = repo.scm_instance()
@@ -590,14 +594,14 @@ def get_repo_file(request, apiuser, repo
         node = ScmModel().get_node(
             repo, commit_id, file_path, extended_info=extended_info,
             content=content, max_file_bytes=max_file_bytes, cache=cache)
+
     except NodeDoesNotExistError:
-        raise JSONRPCError(u'There is no file in repo: `{}` at path `{}` for commit: `{}`'.format(
-            repo.repo_name, file_path, commit_id))
+        raise JSONRPCError(
+            f'There is no file in repo: `{repo.repo_name}` at path `{file_path}` for commit: `{commit_id}`')
     except Exception:
-        log.exception(u"Exception occurred while trying to get repo %s file",
+        log.exception("Exception occurred while trying to get repo %s file",
                       repo.repo_name)
-        raise JSONRPCError(u'failed to get repo: `{}` file at path {}'.format(
-            repo.repo_name, file_path))
+        raise JSONRPCError(f'failed to get repo: `{repo.repo_name}` file at path {file_path}')
 
     return node
 
@@ -619,11 +623,11 @@ def get_repo_fts_tree(request, apiuser, 
         validate_repo_permissions(apiuser, repoid, repo, _perms)
 
     repo_id = repo.repo_id
-    cache_seconds = safe_int(rhodecode.CONFIG.get('rc_cache.cache_repo.expiration_time'))
+    cache_seconds = rhodecode.ConfigGet().get_int('rc_cache.cache_repo.expiration_time')
     cache_on = cache_seconds > 0
 
-    cache_namespace_uid = 'cache_repo.{}'.format(repo_id)
-    region = rc_cache.get_or_create_region('cache_repo', cache_namespace_uid)
+    cache_namespace_uid = 'repo.{}'.format(repo_id)
+    rc_cache.get_or_create_region('cache_repo', cache_namespace_uid)
 
     def compute_fts_tree(cache_ver, repo_id, commit_id, root_path):
         return ScmModel().get_fts_data(repo_id, commit_id, root_path)
@@ -631,11 +635,11 @@ def get_repo_fts_tree(request, apiuser, 
     try:
         # check if repo is not empty by any chance, skip quicker if it is.
         _scm = repo.scm_instance()
-        if _scm.is_empty():
+        if not _scm or _scm.is_empty():
             return []
     except RepositoryError:
         log.exception("Exception occurred while trying to get repo nodes")
-        raise JSONRPCError('failed to get repo: `%s` nodes' % repo.repo_name)
+        raise JSONRPCError(f'failed to get repo: `{repo.repo_name}` nodes')
 
     try:
         # we need to resolve commit_id to a FULL sha for cache to work correctly.
@@ -647,6 +651,7 @@ def get_repo_fts_tree(request, apiuser, 
                 repo_id, commit_id, cache_on, cache_seconds or 0))
 
         tree_files = compute_fts_tree(rc_cache.FILE_TREE_CACHE_VER, repo_id, commit_id, root_path)
+
         return tree_files
 
     except Exception:
@@ -1869,7 +1874,11 @@ def edit_comment(request, apiuser, messa
             raise JSONRPCError('userid is not the same as your user')
 
     comment_author = comment.author.user_id == auth_user.user_id
-    if not (comment.immutable is False and (is_super_admin or is_repo_admin) or comment_author):
+
+    if comment.immutable:
+        raise JSONRPCError("Immutable comment cannot be edited")
+
+    if not (is_super_admin or is_repo_admin or comment_author):
         raise JSONRPCError("you don't have access to edit this comment")
 
     try:
diff --git a/rhodecode/api/views/repo_group_api.py b/rhodecode/api/views/repo_group_api.py
--- a/rhodecode/api/views/repo_group_api.py
+++ b/rhodecode/api/views/repo_group_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/views/server_api.py b/rhodecode/api/views/server_api.py
--- a/rhodecode/api/views/server_api.py
+++ b/rhodecode/api/views/server_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
@@ -342,8 +342,9 @@ def get_method(request, apiuser, pattern
     matches = find_methods(request.registry.jsonrpc_methods, pattern)
 
     args_desc = []
-    if len(matches) == 1:
-        func = matches[matches.keys()[0]]
+    matches_keys = list(matches.keys())
+    if len(matches_keys) == 1:
+        func = matches[matches_keys[0]]
 
         argspec = inspect.getargspec(func)
         arglist = argspec[0]
@@ -356,7 +357,7 @@ def get_method(request, apiuser, pattern
             reversed(arglist), reversed(defaults), fillvalue=default_empty))
         args_desc.append(func_kwargs)
 
-    return matches.keys() + args_desc
+    return matches_keys + args_desc
 
 
 @jsonrpc_method()
diff --git a/rhodecode/api/views/testing_api.py b/rhodecode/api/views/testing_api.py
--- a/rhodecode/api/views/testing_api.py
+++ b/rhodecode/api/views/testing_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/views/user_api.py b/rhodecode/api/views/user_api.py
--- a/rhodecode/api/views/user_api.py
+++ b/rhodecode/api/views/user_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
diff --git a/rhodecode/api/views/user_group_api.py b/rhodecode/api/views/user_group_api.py
--- a/rhodecode/api/views/user_group_api.py
+++ b/rhodecode/api/views/user_group_api.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #