CAM: Improve warning text for improper unit scheme

The previous text suggested to change the scheme in the preferences,
however, the preferences only take effect for new documents. Now, that
we have the "ProjectUnitSystem" in place, the setting for the current
document needs to be changed.

Author: jbaehr

src/Mod/CAM/Path/Main/Gui/JobDlg.py

@@ -65,7 +65,17 @@ def __init__(self, parent=None, sel=None):
                     if idx not in [2, 3, 6]:
                         msg = translate(
                             "CAM_Job",
-                            "The currently selected unit schema: \n     '{}' for this document\n Does not use 'minutes' for velocity values. \n \nCNC machines require feed rate to be expressed in \nunit/minute. To ensure correct G-code: \nSelect a minute-based schema in preferences.\nFor example:\n    'Metric, Small Parts & CNC'\n    'US Customary'\n    'Imperial Decimal'",
+                            ("This document's unit schema:\n"
+                             "    '{}'\n"
+                             "Does not use 'minutes' for velocity values.\n"
+                             "\n"
+                             "CNC machines require feed rate to be expressed in unit/minute. "
+                             "To ensure correct G-code, select a minute-based schema in the "
+                             "document properties.\n"
+                             "For example:\n"
+                             "    'Metric, Small Parts & CNC'\n"
+                             "    'US Customary'\n"
+                             "    'Imperial Decimal'"),
                         ).format(current_schema)
                         header = translate("CAM_Job", "Warning")
                         msgbox = QtGui.QMessageBox(QtGui.QMessageBox.Warning, header, msg)