CLI script to gather environment info (#2699)

* add "info" command to CLI

As a convenience, add the info directive to CLI. Running `python transformers-cli info` will return a string containing the transformers version, platform, python version, PT/TF version and GPU support

* Swap f-strings for .format

Still supporting 3.5 so can't use f-strings (sad face)

* Add reference in issue to CLI

* Add the expected fields to issue template

This way, people can still add the information manually if they want. (Though I fear they'll just ignore it.)

* Remove heading from output

* black-ify

* order of imports

Should ensure isort test passes

* use is_X_available over import..pass

* style

* fix copy-paste bug

* Rename command info -> env

Also adds the command to CONTRIBUTING.md in "Did you find a bug" section

.github/ISSUE_TEMPLATE/bug-report.md

@@ -39,12 +39,14 @@ Steps to reproduce the behavior:
 
 <!-- A clear and concise description of what you would expect to happen. -->
 
-## Environment
-
-* OS:
-* Python version:
-* PyTorch version:
-* `transformers` version (or branch):
-* Using GPU ?
-* Distributed or parallel setup ?
-* Any other relevant information:
+## Environment info
+<!-- You can run the command `python transformers-cli env` and copy-and-paste its output below.
+     Don't forget to fill out the missing fields in that output! -->
+     
+- `transformers` version:
+- Platform:
+- Python version:
+- PyTorch version (GPU?):
+- Tensorflow version (GPU?):
+- Using GPU in script?:
+- Using distributed or parallel set-up in script?:

.github/ISSUE_TEMPLATE/migration.md

@@ -33,16 +33,21 @@ The tasks I am working on is:
     Do not use screenshots, as they are hard to read and (more importantly) don't allow others to copy-and-paste your code.
     -->
 
-## Environment
+## Environment info
+<!-- You can run the command `python transformers-cli env` and copy-and-paste its output below.
+     Don't forget to fill out the missing fields in that output! -->
+ 
+- `transformers` version:
+- Platform:
+- Python version:
+- PyTorch version (GPU?):
+- Tensorflow version (GPU?):
+- Using GPU in script?:
+- Using distributed or parallel set-up in script?:
 
-* OS:
-* Python version:
-* PyTorch version:
+<!-- IMPORTANT: which version of the former library do you use? -->
 * `pytorch-transformers` or `pytorch-pretrained-bert` version (or branch):
-* `transformers` version (or branch):
-* Using GPU?
-* Distributed or parallel setup?
-* Any other relevant information:
+
 
 ## Checklist