Fix the following pylint warning instances:

ynl_gen_c.py:575:15: E0606: Possibly using variable 'mem' before
assignment (possibly-used-before-assignment)

ynl_gen_c.py:888:0: R1707: Disallow trailing comma tuple
(trailing-comma-tuple)

ynl_gen_c.py:944:21: C0209: Formatting a regular string which could be an
f-string (consider-using-f-string)

ynl_gen_c.py:1450:14: C1802: Do not use `len(SEQUENCE)` without comparison
to determine if a sequence is empty (use-implicit-booleaness-not-len)

ynl_gen_c.py:1688:13: W1514: Using open without explicitly specifying an
encoding (unspecified-encoding)

ynl_gen_c.py:3446:0: C0325: Unnecessary parens after '=' keyword
(superfluous-parens)

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index 5f079a74c8d1..c823ccf2b75c 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py
@@ -571,6 +571,8 @@ class TypeBinary(Type):
             mem = 'NLA_POLICY_MIN_LEN(' + self.get_limit_str('min-len') + ')'
         elif 'max-len' in self.checks:
             mem = 'NLA_POLICY_MAX_LEN(' + self.get_limit_str('max-len') + ')'
+        else:
+            raise Exception('Failed to process policy check for binary type')
 
         return mem
 
@@ -885,7 +887,7 @@ class TypeIndexedArray(Type):
                 f"for (i = 0; i < {var}->{ref}_count.{self.c_name}; i++)",
                 f'{self.nested_render_name}_free(&{var}->{ref}{self.c_name}[i]);',
             ]
-        lines += f"free({var}->{ref}{self.c_name});",
+        lines += (f"free({var}->{ref}{self.c_name});",)
         return lines
 
 class TypeNestTypeValue(Type):
@@ -941,9 +943,8 @@ class TypeSubMessage(TypeNest):
         else:
             sel_var = f"{var}->{sel}"
         get_lines = [f'if (!{sel_var})',
-                     'return ynl_submsg_failed(yarg, "%s", "%s");' %
-                        (self.name, self['selector']),
-                    f"if ({self.nested_render_name}_parse(&parg, {sel_var}, attr))",
+                     f'return ynl_submsg_failed(yarg, "{self.name}", "{self['selector']}");',
+                     f"if ({self.nested_render_name}_parse(&parg, {sel_var}, attr))",
                      "return YNL_PARSE_CB_ERROR;"]
         init_lines = [f"parg.rsp_policy = &{self.nested_render_name}_nest;",
                       f"parg.data = &{var}->{self.c_name};"]
@@ -1447,7 +1448,7 @@ class Family(SpecFamily):
         attr_set_queue = list(self.root_sets.keys())
         attr_set_seen = set(self.root_sets.keys())
 
-        while len(attr_set_queue):
+        while attr_set_queue:
             a_set = attr_set_queue.pop(0)
             for attr, spec in self.attr_sets[a_set].items():
                 if 'nested-attributes' in spec:
@@ -1685,7 +1686,7 @@ class CodeWriter:
         if not self._overwrite and os.path.isfile(self._out_file):
             if filecmp.cmp(self._out.name, self._out_file, shallow=False):
                 return
-        with open(self._out_file, 'w+') as out_file:
+        with open(self._out_file, 'w+', encoding='utf-8') as out_file:
             self._out.seek(0)
             shutil.copyfileobj(self._out, out_file)
             self._out.close()
@@ -3443,7 +3444,7 @@ def main():
         print(exc)
         os.sys.exit(1)
 
-    cw = CodeWriter(BaseNlLib(), args.out_file, overwrite=(not args.cmp_out))
+    cw = CodeWriter(BaseNlLib(), args.out_file, overwrite=not args.cmp_out)
 
     _, spec_kernel = find_kernel_root(args.spec)
     if args.mode == 'uapi' or args.header:
-- 
2.52.0