ArcMap crashes after using a custom toolbar

GordonD

I attempted to write a custom toolbar similar to this one, but in my version clicking anywhere within a data frame opens a new tab of King County iMap that points to the location you clicked. Here is my code:

<SPAN class="keyword token">import</SPAN> arcpy
<SPAN class="keyword token">import</SPAN> pythonaddins
<SPAN class="keyword token">import</SPAN> webbrowser

<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">ToolClass</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="string token">"""Implementation for Open_iMap_addin.tool (Tool)"""</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">__init__</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        self<SPAN class="punctuation token">.</SPAN>enabled <SPAN class="operator token">=</SPAN> <SPAN class="token boolean">True</SPAN>
        self<SPAN class="punctuation token">.</SPAN>shape <SPAN class="operator token">=</SPAN> <SPAN class="string token">"NONE"</SPAN> <SPAN class="comment token"># Can set to "Line", "Circle" or "Rectangle" for interactive shape drawing and to activate the onLine/Polygon/Circle event sinks.</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">onMouseDownMap</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> x<SPAN class="punctuation token">,</SPAN> y<SPAN class="punctuation token">,</SPAN> button<SPAN class="punctuation token">,</SPAN> shift<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"CURRENT"</SPAN><SPAN class="punctuation token">)</SPAN>
        df <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListDataFrames<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
        point <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>PointGeometry<SPAN class="punctuation token">(</SPAN>arcpy<SPAN class="punctuation token">.</SPAN>Point<SPAN class="punctuation token">(</SPAN>x<SPAN class="punctuation token">,</SPAN>y<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">,</SPAN>arcpy<SPAN class="punctuation token">.</SPAN>SpatialReference<SPAN class="punctuation token">(</SPAN>df<SPAN class="punctuation token">.</SPAN>spatialReference<SPAN class="punctuation token">.</SPAN>PCSCode<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        newPoint <SPAN class="operator token">=</SPAN> point<SPAN class="punctuation token">.</SPAN>projectAs<SPAN class="punctuation token">(</SPAN>arcpy<SPAN class="punctuation token">.</SPAN>SpatialReference<SPAN class="punctuation token">(</SPAN><SPAN class="number token">4326</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN>x<SPAN class="punctuation token">,</SPAN>y<SPAN class="punctuation token">)</SPAN>
        <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN>str<SPAN class="punctuation token">(</SPAN>newPoint<SPAN class="punctuation token">.</SPAN>centroid<SPAN class="punctuation token">.</SPAN>X<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">", "</SPAN> <SPAN class="operator token">+</SPAN>str<SPAN class="punctuation token">(</SPAN>newPoint<SPAN class="punctuation token">.</SPAN>centroid<SPAN class="punctuation token">.</SPAN>Y<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        webbrowser<SPAN class="punctuation token">.</SPAN>open<SPAN class="punctuation token">(</SPAN><SPAN class="string token">'https://gismaps.kingcounty.gov/iMap/?center='</SPAN><SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>newPoint<SPAN class="punctuation token">.</SPAN>centroid<SPAN class="punctuation token">.</SPAN>X<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">'%2C'</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>newPoint<SPAN class="punctuation token">.</SPAN>centroid<SPAN class="punctuation token">.</SPAN>Y<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">'&level=19'</SPAN><SPAN class="punctuation token">,</SPAN> new<SPAN class="operator token">=</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

The tool works, but my ArcMap crashes immediately after opening iMap and I get the following error: 

Any idea why this might be happening?