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provision: Give a better error message; ensure the correct version of pip. #128

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provision: Give a better error message; ensure the correct version of pip. #128

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provision: Give a clear error message when virtualenv is missing.
alenavolk Sep 27, 2017
cdb27f4
provision: Make sure the correct version of pip is installed.
alenavolk Sep 28, 2017
ec1ccd9
provision: Remove unnecessary imports.
alenavolk Sep 28, 2017
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14 changes: 11 additions & 3 deletions tools/provision
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Original file line number Diff line number Diff line change
Expand Up @@ -24,10 +24,18 @@ the Python version this command is executed with."""

venv_dir = os.path.join(base_dir, venv_name)
if not os.path.isdir(venv_dir):
if subprocess.call(['virtualenv', '-p', python_interpreter, venv_dir]):
raise OSError("The command `virtualenv -p {} {}` failed. Virtualenv not created!"
.format(python_interpreter, venv_dir))
try:
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Rather than try-except, there is a way to detect specifically whether virtualenv has been installed. Ref: https://stackoverflow.com/questions/1871549/python-determine-if-running-inside-virtualenv/1883251#1883251.

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Sounds great, I'll look into that. Thanks for the feedback!

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Unfortunately, I don't see how this can be applied here. This is a good way to check whether the code is running inside a virtual environment. What would be helpful in this case is a way to check whether the virtualenv package is installed (before using it to create an environment).

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@rht rht Sep 28, 2017 •
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Here is how it is checked in one of the tool in the Zulip webapp/server:
https://github.com/zulip/zulip/blob/master/tools/update-locked-requirements#L4-L7
If the venv_dir is known, a check along this line can be done.

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@alenavolk alenavolk Sep 29, 2017 •
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This is already being done one line above:

if not os.path.isdir(venv_dir):
    ...

But what if the environment doesn't exist? We run the following code to create it:

subprocess.call(['virtualenv', '-p', python_interpreter, venv_dir])

To do it successfully we need to have the virtualenv package installed. On Ubuntu it can be done by running this command in the terminal:

sudo apt-get install python-virtualenv

If we make the subprocess call before the virtualenv package is installed the script will exit with an error and print the traceback I included above.

What I'm trying to do here is to replace this traceback with an error message that tells people exactly what's going on: they need to install the package to run the script.

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I agree with the idea of checking if virtualenv is installed as the first step, makes the logic easier. Instead of which virtualenv, I suggest checking the exit code of command -v virtualenv, since its a shell built-in and part of posix.

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@alenavolk alenavolk Sep 29, 2017 •
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@rht @derAnfaenger Thanks for the suggestions! I agree that checking if the virtualenv package is installed before using it makes more sense than a try-except block. I'll make use of command -v virtualenv too.

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@alenavolk alenavolk Sep 29, 2017 •
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Hm, the subprocess call fails when I use command -v virtualenv:

Traceback (most recent call last):
  File "./tools/provision", line 76, in <module>
    main()
  File "./tools/provision", line 26, in main
    if subprocess.call(['command', '-v', 'virtualenv']):
  File "/usr/lib/python2.7/subprocess.py", line 522, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

Should I keep using which virtualenv or wrap it in a try-except block, perhaps?

try:
    subprocess.call(['command', '-v', 'virtualenv'])
except OSError:
    print("{red}Please install the virtualenv package and try again.{end_format}"
                  .format(red='\033[91m', end_format='\033[0m'))
    sys.exit(1)

if subprocess.call(['virtualenv', '-p', python_interpreter, venv_dir]):
    ...

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This discussion had a lot of suggestions that didn't actually work. @rht next time, I'd encourage you to read the code more closely before commenting; e.g. https://stackoverflow.com/questions/1871549/python-determine-if-running-inside-virtualenv/1883251#1883251 was totally irrelevant to the problem at hand :)

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(my mistake :( )

return_code = subprocess.call(['virtualenv', '-p', python_interpreter, venv_dir])
except OSError:
if subprocess.call(['which', 'virtualenv']):
print("{red}Please install the virtualenv package and try again.{end_format}"
.format(red='\033[91m', end_format='\033[0m'))
sys.exit(1)
raise
else:
if return_code:
raise OSError("The command `virtualenv -p {} {}` failed. Virtualenv not created!"
.format(python_interpreter, venv_dir))
print("New virtualenv created.")
else:
print("Virtualenv already exists.")
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