Draft: Fix LGTM 'test for equality' warning (#4969)

* Draft: Fix LGTM 'test for equality' warning

ref: https://lgtm.com/projects/g/FreeCAD/FreeCAD/alerts/?mode=tree&ruleFocus=7900090

* FEM: source comment typo fixes

src/Mod/Draft/draftutils/units.py

@@ -95,7 +95,7 @@ def display_external(internal_value,
     if dim == 'Length':
         q = App.Units.Quantity(internal_value, App.Units.Length)
         if not unit:
-            if decimals == None and showUnit:
+            if decimals is None and showUnit:
                 return q.UserString
 
             conversion = q.getUserPreferred()[1]

src/Mod/Fem/femexamples/truss_3d_cs_circle_ele_seg3.py

@@ -64,7 +64,7 @@ https://forum.freecadweb.org/viewtopic.php?f=13&t=59239&start=100#p521220
 
 Z88 official example 2, crane beam
 - nonsway (on x deformation on both support)
-- in pratical engineering one would let the truss breathe on one side
+- in practical engineering one would let the truss breathe on one side
 - max deflection CalxuliX: 8.22 mm  # but it needs four seg3 elements foreach bar
 - max deflection Mystran : x.xx mm
 - max deflection Z88 : 8.19 mm  # one seg2 truss element foreach bar
@@ -93,7 +93,7 @@ def setup(doc=None, solvertype="ccxtools"):
     if FreeCAD.GuiUp:
         load_line.ViewObject.hide()
 
-    # commands where generated by Pyhon out of the original Z88 Mesh obj data
+    # commands where generated by Python out of the original Z88 Mesh obj data
     v1 = vec(0.0, 2000.0, 0.0)
     v2 = vec(0.0, 0.0, 0.0)
     v3 = vec(1000.0, 1000.0, 2000.0)