gh-35697: cylint: remove imports in misc/
    
<!-- Please provide a concise, informative and self-explanatory title.
-->
<!-- Don't put issue numbers in the title. Put it in the Description
below. -->
<!-- For example, instead of "Fixes #12345", use "Add a new method to
multiply two integers" -->

### 📚 Description

remove unused imports found by cython-lint in `misc` folder

also one unused variable is removed

<!-- Describe your changes here in detail. -->
<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes #12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. It should be `[x]` not `[x
]`. -->

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on
- #12345: short description why this is a dependency
- #34567: ...
-->

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: #35697
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe

Author: Release Manager

src/sage/misc/binary_tree.pyx

@@ -63,7 +63,6 @@ cdef object binary_tree_get(binary_tree_node *self, int key):
 
 cdef object binary_tree_delete(binary_tree_node *self, int key):
     cdef object t
-    cdef binary_tree_node *cur
     if self.key > key:
         if self.left == NULL:
             return None

src/sage/misc/fpickle.pyx

@@ -5,7 +5,6 @@ Function pickling
 
 REFERENCE: The python cookbook.
 """
-
 import copyreg
 import pickle
 import sys
@@ -91,6 +90,7 @@ def pickle_function(func):
     """
     return pickle.dumps(func.__code__)
 
+
 def unpickle_function(pickled):
     """
     Unpickle a pickled function.
@@ -106,15 +106,16 @@ def unpickle_function(pickled):
     return types.FunctionType(recovered, globals())
 
 
-
 def call_pickled_function(fpargs):
     import sage.all
-    from sage.misc.fpickle import unpickle_function
+    from sage.misc.fpickle import unpickle_function  # used below
     (fp, (args, kwds)) = fpargs
-    f = eval("unpickle_function(fp)", sage.all.__dict__, {'fp':fp})
-    res = eval("f(*args, **kwds)",sage.all.__dict__, {'args':args, 'kwds':kwds, 'f':f})
+    f = eval("unpickle_function(fp)", sage.all.__dict__, {'fp': fp})
+    res = eval("f(*args, **kwds)", sage.all.__dict__,
+               {'args': args, 'kwds': kwds, 'f': f})
     return ((args, kwds), res)
 
+
 # The following four methods are taken from twisted.persisted.styles - the
 # import of twisted.persisted.styles takes a long time and we do not use
 # most functionality it provides
@@ -128,11 +129,11 @@ def pickleMethod(method):
 
 
 def unpickleMethod(im_name,
-                    __self__,
-                    im_class):
+                   __self__,
+                   im_class):
     'support function for copyreg to unpickle method refs'
     try:
-        unbound = getattr(im_class,im_name)
+        unbound = getattr(im_class, im_name)
         if __self__ is None:
             return unbound
 
@@ -154,21 +155,25 @@ def unpickleMethod(im_name,
                                  __self__)
         return bound
 
+
 copyreg.pickle(types.MethodType,
-                pickleMethod,
-                unpickleMethod)
+               pickleMethod,
+               unpickleMethod)
 
 oldModules = {}
 
+
 def pickleModule(module):
     'support function for copyreg to pickle module refs'
     return unpickleModule, (module.__name__,)
 
+
 def unpickleModule(name):
     'support function for copyreg to unpickle module refs'
     if name in oldModules:
         name = oldModules[name]
-    return __import__(name,{},{},'x')
+    return __import__(name, {}, {}, 'x')
+
 
 copyreg.pickle(types.ModuleType,
                pickleModule,

src/sage/misc/misc_c.pyx

@@ -23,8 +23,6 @@ AUTHORS:
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-import sys
-
 from cpython.sequence cimport *
 from cpython.list cimport *
 from cpython.tuple cimport *

src/sage/misc/parser.pyx

@@ -20,8 +20,6 @@ AUTHOR:
 #                  https://www.gnu.org/licenses/
 # ***************************************************************************
 
-from libc.string cimport strchr
-from cpython.bytes cimport PyBytes_FromStringAndSize
 from cpython.list cimport PyList_Append
 
 import math
@@ -1095,4 +1093,4 @@ cdef class LookupNameMaker:
         except KeyError:
             if self.fallback is not None:
                 return self.fallback(name)
-            raise NameError("Unknown variable: '{}'".format(name))
+            raise NameError(f"Unknown variable: '{name}'")

src/sage/misc/randstate.pyx

@@ -419,7 +419,6 @@ import os
 import time
 import weakref
 import random as _random
-import sys
 
 use_urandom = False
 # Check whether os.urandom() works.
@@ -713,7 +712,6 @@ cdef class randstate:
             if self._gap_saved_seed is not None:
                 mersenne_seed, classic_seed = self._gap_saved_seed
             else:
-                import sage.rings.integer_ring as integer_ring
                 from sage.rings.integer_ring import ZZ
                 seed = ZZ.random_element(long(1)<<128)
                 classic_seed = seed

src/sage/misc/session.pyx

@@ -61,12 +61,11 @@ AUTHOR:
 #       Copyright (C) 2007,2010 William Stein <[email protected]>
 #  Distributed under the terms of the GNU General Public License (GPL)
 #  The full text of the GPL is available at:
-#                  http://www.gnu.org/licenses/
+#                  https://www.gnu.org/licenses/
 #############################################################################
 
 # Standard python imports
 import builtins
-import os
 import types
 
 # We want the caller's locals, but locals() is emulated in Cython

src/sage/misc/weak_dict.pyx

@@ -118,15 +118,13 @@ See :trac:`13394` for a discussion of some of the design considerations.
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-import weakref
 from weakref import KeyedRef
 from copy import deepcopy
 
 from cpython.dict cimport PyDict_SetItem, PyDict_Next
 from cpython.tuple cimport PyTuple_GET_SIZE, PyTuple_New
 from cpython.weakref cimport PyWeakref_NewRef
-from cpython.object cimport PyObject_Hash
-from cpython.ref cimport Py_INCREF, Py_XINCREF, Py_XDECREF
+from cpython.ref cimport Py_INCREF
 from sage.cpython.dict_del_by_value cimport *
 
 from sage.misc.superseded import deprecation