pip install failure for cryptography, gnureadline

[dieter]

Pietro Paolini <pietro.paolini at ocado.com> writes:
> ...
> I am not really familiar with the Py subsystem, even though I have got some
> guidance from some colleague, I am getting stuck when installing a list of
> packages contained in a file, running such command :
>
>
> pip install -r /home/pietro/projects/cloud-provisioning/requirements.txt
>
> Brings me :
>
>
> Collecting docutils>=0.10 (from botocore<1.4.0,>=1.3.0->boto3==1.2.3->-r
> /home/pietro/projects/cloud-provisioning/requirements.txt (line 9))
> Building wheels for collected packages: cryptography, gnureadline
>   Running setup.py bdist_wheel for cryptography: started
>   Running setup.py bdist_wheel for cryptography: finished with status
> 'error'
>   Complete output from command
> ....
> src/cryptography/hazmat/bindings/__pycache__/_Cryptography_cffi_d5a71fe5xf53f5318.c:1944:15:
> error: ‘SSLv3_method’ redeclared as different kind of symbol
>    SSL_METHOD* (*SSLv3_method)(void) = NULL;
>                  ^
>   In file included from
> src/cryptography/hazmat/bindings/__pycache__/_Cryptography_cffi_d5a71fe5xf53f5318.c:294:0:
>   /usr/include/openssl/ssl.h:1892:19: note: previous declaration of
> ‘SSLv3_method’ was here
>    const SSL_METHOD *SSLv3_method(void);  /* SSLv3 */
>                      ^

This indicates that the "cryptography" version does not fit
with your "openssl" version: "openssl" defines "SSLv3_method"
as a function returning a constant pointer to an "SSL_METHOD",
while "cryptography" defines it as a pointer to such a function.

I would contact the "cryptography" author.