PTVSD exceptions are not shown to the user - makes it look like debug cell doesn't work

[luabud]

Environment data

• VS Code version: 1.36.1
• Extension version (available under the Extensions sidebar): 2019.9.28224-dev
• OS and version: Windows 10
• Python version (& distribution if applicable, e.g. Anaconda): 3.7.3
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): N/A
• Relevant/affected Python packages and their versions: jupyter notebook 5.7.2

Steps to reproduce:

I used this file:

#%%
import matplotlib.pyplot as plt
import numpy as np 

#%%
x = np.array([5,2,4,6])
y = np.array(['a','b','c','d'])

#%%
plt.bar(y,x)
plt.show()

I added a breakpoint to plt.bar(y,x) and hit "debug cell" after running the first two cells, but it's not stopping at the breakpoint.

Logs

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

Nothing relevant showed up there for this

Output

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help; turn on source maps to make any tracebacks be useful by running Enable source map support for extension debugging)

[rchiodo]

Where is it stopping? It should stop at plt.bar(), the first line.

[rchiodo]

That's what it does for me.

[rchiodo]

@luabud 's problem was a PTVSD env variable being set that was causing PTVSD to crash on attach.

We should at least log this failure, and/or tell the user why the debugger didn't start.