update error message for shading=flat

Author: vivekvedant

lib/matplotlib/axes/_axes.py

@@ -5749,8 +5749,8 @@ def _pcolorargs(self, funcname, *args, shading='auto', **kwargs):
         if shading == 'flat':
             if (Nx, Ny) != (ncols + 1, nrows + 1):
                 raise TypeError(f"Dimensions of X({Nx}) and y({Ny}) should"
-                                f"be one larger than C{C.shape}"
-                                f"see help({funcname})")
+                                f" be one larger than C {C.shape} while using"
+                                f" shading='flat' see help({funcname})")
         else:    # ['nearest', 'gouraud']:
             if (Nx, Ny) != (ncols, nrows):
                 raise TypeError('Dimensions of C %s are incompatible with'