gh-35165: activate W293 and E714 in pyx files
    
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### 📚 Description

This fixes and activate the pycodestyle warnings

W293: blank line contains whitespace

and

E714: Test for object identity should be 'is not'

in all .pyx files inside src/sage

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URL: #35165
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/graphs/graph_coloring.pyx

@@ -1498,11 +1498,11 @@ def _vizing_edge_coloring(g):
 
     INPUT:
 
-    - ``g`` -- a graph.
+    - ``g`` -- a graph
 
     OUTPUT:
 
-    - Returns a partition of the edge set into at most `\Delta + 1` matchings.
+    a partition of the edge set into at most `\Delta + 1` matchings
 
     .. SEEALSO::
 
@@ -1512,7 +1512,7 @@ def _vizing_edge_coloring(g):
     ALGORITHM:
 
     This function's implementation is based on the algorithm described at [MG1992]_
-    
+
     EXAMPLES:
 
     Coloring the edges of the Petersen Graph::

src/sage/matrix/matrix_polynomial_dense.pyx

@@ -3974,7 +3974,7 @@ cdef class Matrix_polynomial_dense(Matrix_generic_dense):
             P = self.minimal_approximant_basis(orders,shifts,True,normal_form)
             row_indices = []
             for i in range(m):
-                if P[i,i].degree() + shifts[i] <= degree_bound:
+                if P[i, i].degree() + shifts[i] <= degree_bound:
                     row_indices.append(i)
             return P[row_indices,:]
 
@@ -4000,6 +4000,6 @@ cdef class Matrix_polynomial_dense(Matrix_generic_dense):
             P = self.minimal_approximant_basis(orders,shifts,False,normal_form)
             column_indices = []
             for j in range(n):
-                if P[j,j].degree() + shifts[j] <= degree_bound:
+                if P[j, j].degree() + shifts[j] <= degree_bound:
                     column_indices.append(j)
             return P[:,column_indices]

src/sage/modular/hypergeometric_misc.pyx

@@ -5,6 +5,7 @@ significantly from Cythonization.
 from cpython cimport array
 from cysignals.signals cimport sig_check
 
+
 cpdef hgm_coeffs(long long p, int f, int prec, gamma, m, int D,
                  gtable, int gtable_prec, bint use_longs):
     r"""
@@ -24,9 +25,9 @@ cpdef hgm_coeffs(long long p, int f, int prec, gamma, m, int D,
         sage: D = 1
         sage: hgm_coeffs(7, 1, 2, gamma, [0]*6, D, gtable, prec, False)
         [7, 2*7, 6*7, 7, 6, 4*7]
-        
+
     Check issue from :trac:`28404`::
-    
+
         sage: H = Hyp(cyclotomic=[[10,2],[1,1,1,1,1]])
         sage: u = H.euler_factor(2,79) # indirect doctest
         sage: u.reverse().is_weil_polynomial()
@@ -116,7 +117,7 @@ cpdef hgm_coeffs(long long p, int f, int prec, gamma, m, int D,
                 if flip:
                     gv = -gv
                 if use_longs:
-                    w2 = gtab2[r1] # cast to long long to avoid overflow
+                    w2 = gtab2[r1]  # cast to long long to avoid overflow
                     if gv > 0: 
                         for j in range(gv):
                             w = w * w2 % q2

src/tox.ini

@@ -119,12 +119,13 @@ description =
     # E721: do not compare types, use isinstance()
     # E722: do not use bare except, specify exception instead
     # W291: trailing whitespace
+    # W293: blank line contains whitespace
     # W391: blank line at end of file
     # W605: invalid escape sequence ‘x’
     # See https://pycodestyle.pycqa.org/en/latest/intro.html#error-codes
 deps = pycodestyle
 commands = pycodestyle --select E111,E211,E306,E401,E701,E702,E703,W291,W391,W605,E711,E712,E713,E721,E722 {posargs:{toxinidir}/sage/}
-       pycodestyle --select E111,E306,E401,E703,W391,W605,E712,E713,E721,E722 --filename *.pyx {posargs:{toxinidir}/sage/}
+       pycodestyle --select E111,E306,E401,E703,W293,W391,W605,E712,E713,E714,E721,E722 --filename *.pyx {posargs:{toxinidir}/sage/}
 
 [pycodestyle]
 max-line-length = 160