Don't autoimport FigureWidget unless ipywidgets is installed and >= 7.0.0 (#1425)

* Don't autoimport FigureWidget unless ipywidgets is installed and >= 7.0.0
* Remove LooseVersion and ipywidgets from graph_objs namespace

Author: jonmmease

Diff for: codegen/__init__.py

@@ -235,10 +235,13 @@ def perform_codegen():
     optional_figure_widget_import = """
 try:
     import ipywidgets
-    from ._figurewidget import FigureWidget
+    from distutils.version import LooseVersion
+    if LooseVersion(ipywidgets.__version__) >= LooseVersion('7.0.0'):
+        from ._figurewidget import FigureWidget
+    del LooseVersion
+    del ipywidgets
 except ImportError:
     pass
-
 """
     root_datatype_imports.append(optional_figure_widget_import)
 

Diff for: plotly/basewidget.py

@@ -15,6 +15,7 @@
 from .serializers import custom_serializers
 from .version import __frontend_version__
 
+
 @widgets.register
 class BaseFigureWidget(BaseFigure, widgets.DOMWidget):
     """

Diff for: plotly/graph_objs/__init__.py

@@ -79,10 +79,13 @@
 
 try:
     import ipywidgets
-    from ._figurewidget import FigureWidget
+    from distutils.version import LooseVersion
+    if LooseVersion(ipywidgets.__version__) >= LooseVersion('7.0.0'):
+        from ._figurewidget import FigureWidget
+    del LooseVersion
+    del ipywidgets
 except ImportError:
     pass
-
 from ._deprecations import (
     Data, Annotations, Frames, AngularAxis, Annotation, ColorBar, Contours,
     ErrorX, ErrorY, ErrorZ, Font, Legend, Line, Margin, Marker, RadialAxis,