fix #48 Attached Placement error in FC 0.18.4

lattice2Compatibility.py

@@ -1,10 +1,37 @@
 import FreeCAD as App
 
+def get_fc_version():
+    """returns tuple like (0,18,4,16154) for 0.18.4 release, and (0,19,0,18234) for pre builds"""
+    # ['0', '18', '4 (GitTag)', 'git://github.com/FreeCAD/FreeCAD.git releases/FreeCAD-0-18', '2019/10/22 16:53:35', 'releases/FreeCAD-0-18', '980bf9060e28555fecd9e3462f68ca74007b70f8']
+    # ['0', '19', '18234 (Git)', 'git://github.com/FreeCAD/FreeCAD.git master', '2019/09/15 20:43:17', 'master', '3af5d97e9b2a60823815f662aba25422c4bc45bb']
+    strmaj, strmi, strrev = App.Version()[0:3]
+    maj, mi = int(strmaj), int(strmi)
+    submi, rev = 0, 0
+    if '(GitTag)' in strrev:
+        submi = int(strrev.split(" ")[0])
+    elif '(Git)' in strrev:
+        try:
+            rev = int(strrev.split(" ")[0])
+        except Exception as err:
+            App.Console.PrintWarning(u"Lattice2 failed to detect FC version number.\n"
+                                     "    {err}\n".format(err= str(err)))
+            rev = 19207 #assume fairly modern
+    if rev < 100:
+        if mi == 17:
+            rev = 13544
+        elif mi == 18:
+            rev = 16154
+        else:
+            rev = 19207 #assume fairly modern
+            App.Console.PrintWarning(u"Lattice2 failed to detect FC version number: revision is zero / too low, minor version is unexpected.")
+    return (maj, mi, submi, rev)
+
+
 try:
-    rev_number = int(App.Version()[2].split(" ")[0])
+    rev_number = get_fc_version()[3]
 except Exception as err:
+    App.Console.PrintError(str(err))
     rev_number = 10000000
-    del err
 
 attach_extension_era = rev_number >= 9177