TypeError: cannot return std::string from Unicode object

[jyder4@…]

Error was occured when I click one of the milestone from table of milestone at dashboard.

How to Reproduce

While doing a GET operation on /mdashboard/4.3.1.3, Trac issued an internal error.

(please provide additional details here)

Request parameters:

{'id': u'4.3.1.3', 'imagename': None}

System Information

Trac	0.11dev-r6425
Python	2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)]
setuptools	0.6c7
SQLite	3.5.2
pysqlite	2.4.0
Genshi	0.5dev-r789
mod_python	3.3.1
Pygments	0.9
Subversion	1.4.6 (r28521)

Python Traceback

Traceback (most recent call last):
  File "g:\python25\lib\site-packages\Trac-0.11dev_r6425-py2.5.egg\trac\web\main.py", line 406, in _dispatch_request
    dispatcher.dispatch(req)
  File "g:\python25\lib\site-packages\Trac-0.11dev_r6425-py2.5.egg\trac\web\main.py", line 195, in dispatch
    resp = chosen_handler.process_request(req)
  File "build\bdist.win32\egg\tracmetrixplugin\mdashboard.py", line 431, in process_request
    return self._render_view(req, db, milestone)
  File "build\bdist.win32\egg\tracmetrixplugin\mdashboard.py", line 557, in _render_view
    create_cumulative_chart(self.env, milestone, numdates, tkt_cumulative_table)
  File "build\bdist.win32\egg\tracmetrixplugin\mdashboard.py", line 324, in create_cumulative_chart
    fig.savefig(path)
  File "G:\Python25\Lib\site-packages\matplotlib\figure.py", line 782, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "G:\Python25\Lib\site-packages\matplotlib\backend_bases.py", line 1195, in print_figure
    **kwargs)
  File "G:\Python25\Lib\site-packages\matplotlib\backends\backend_agg.py", line 397, in print_png
    self.get_renderer()._renderer.write_png(filename, self.figure.dpi.get())
TypeError: cannot return std::string from Unicode object

[raymond.wooninck@…]

I had the same problem and I was able to fix it by playing with the version of the matplotlib. I am running TRAC on Windows 2003 under Apache 2.2 and I had installed all latest versions of the indicated requirements. This lead to the same error as you described. I tried to lower the versions of all the requirements to the recommended version, but was unable to do this for Pygtk. With matplotlib 0.87-7 I received a different error, but now I am running with version 0.90.0 and this one solves the errors.

It might be worth it to try matplotlib versions lower than 0.91. What I found on the internet is that with this version a change was made how Unicode fonts are translated.

Raymond

[Richard Wall]

Replying to raymond.wooninck@cchellenic.com:

I had the same problem and I was able to fix it by playing with the version of the matplotlib.

<snip>

It might be worth it to try matplotlib versions lower than 0.91. What I found on the internet is that with this version a change was made how Unicode fonts are translated.

Thanks for the pointer. Have just installed TracMetrixPlugin with Trac 0.11.1 on Ubuntu Hardy and got the same error. I manually applied the following change to python2.5-matplotlib (0.91.2-0ubuntu1) and the page and graph work again. See:

• ​http://matplotlib.svn.sourceforge.net/viewvc/matplotlib/branches/v0_91_maint/lib/matplotlib/backends/backend_agg.py?r1=4874&r2=4873&pathrev=4874

branches/v0_91_maint/lib/matplotlib/backends/backend_agg.py

@@ -394 +394 @@
 
     def print_png(self, filename, *args, **kwargs):
         self.draw()
+        filename = str(filename) # until we figure out unicode handling
         self.get_renderer()._renderer.write_png(filename, self.figure.dpi.get())
 

[Richard Wall]

Note duplicate ticket #2900

[Bhuricha Deen Sethanandha]

I just add the code to use Yahoo chart to plot instead of the Matplotlib. This problem should be fixed.