fix the famous WeakSet keyError bug

[chengs]

This PR fixes #596 #548 #553, by checking the existence of an instance before removing it from tqdm._instances (WeakSet)
Another solution to fix them is to ignore the KeyError in the following code.

• fix error in test_perf.

I think I almost find why this problem occurs.
@casperdcl See this
v4.19.1...tqdm:v4.24.0

It is highly possible that, the problem is because of this part in _tqdm.py

In v4.19, when removing an instance from WeakSet, the KeyError is ignored.
Magically, now it will raise an error. (well, I don't have time to check why someone changes this to raise an error).

However, we can avoid this keyError.
It seems in python2, when tqdm is called with for like this

for _ in trange(10):
   break

py2 will magically collect the hidden object of trange(10) after break, which causes this keyError.
I say this because this code works well.

pbar = tqdm(range(10))
for i in pbar:
    if i==2:
        break

So, it may happen that the tqdm._instances(WeakSet) does not know the instance is already removed, but it still try to remove the instance and causes the keyError. We can add a check step before the removal.

[codecov-io]

Codecov Report

Merging #607 into master will decrease coverage by 0.23%.
The diff coverage is 92.3%.

@@            Coverage Diff             @@
##           master     #607      +/-   ##
==========================================
- Coverage   98.87%   98.63%   -0.24%     
==========================================
  Files           9       10       +1     
  Lines         709      731      +22     
  Branches      127      130       +3     
==========================================
+ Hits          701      721      +20     
- Misses          5        6       +1     
- Partials        3        4       +1

[chengs]

v4.19.1...tqdm:v4.24.0
v4.20.0...tqdm:v4.24.0

Until 4.20, it is ok.
It's because of a commit in v4.21. @casperdcl, please check these commits

• d7ccbbd#diff-35aa74e5cefc63c038a9a0f55b5166cd
• 06e25b3#diff-35aa74e5cefc63c038a9a0f55b5166cd

They changed the behavior of keyError.

[jgsogo]

Hi!

How is this PR going? Some of our users have come across another error when installing our app, Conan, due to the tqdm dependency (here is our open issue: conan-io/conan#3728, here is the one in your repo: #460).

We would want to know if solving this issue will allow us to upgrade the dependency and solve both of them... or maybe we should downgrade tqdm to <4.19.1.

Thanks!

[casperdcl]

#460 is unrelated. I hope to get around to reviewing this PR and all my other backlog soon

[casperdcl]

getting there...