Fix Docker build

At some point Alpine switched from openssl to libressl. For some reason
this caused an error to appear during last week:

    Step 17/24 : RUN apk add [...]

     ---> Running in 52e7e742d29e
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
    ERROR: unsatisfiable constraints:
      openssl-dev-1.0.2o-r0:
	conflicts:
		   libressl-dev-2.6.3-r0[pc:libcrypto=1.0.2o]
		   libressl-dev-2.6.3-r0[pc:libssl=1.0.2o]
		   libressl-dev-2.6.3-r0[pc:openssl=1.0.2o]
      libressl-dev-2.6.3-r0:
	conflicts:
		   openssl-dev-1.0.2o-r0[pc:libcrypto=2.6.3]
		   openssl-dev-1.0.2o-r0[pc:libssl=2.6.3]
		   openssl-dev-1.0.2o-r0[pc:openssl=2.6.3]
	satisfies:
		   postgresql-dev-10.4-r0[libressl-dev]
      build-dependencies-0:
	masked in: cache
	satisfies: world[build-dependencies]

Switching to libressl solved that issue but the the cryptography python package
build was failing:

    gcc -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/local/include/python3.5m -c build/temp.linux-x86_64-3.5/_openssl.c -o build/temp.linux-x86_64-3.5/build/temp.linux-x86_64-3.5/_openssl.o
    In file included from /usr/include/openssl/x509.h:595:0,
                     from /usr/include/openssl/engine.h:96,
                     from build/temp.linux-x86_64-3.5/_openssl.c:567:
    build/temp.linux-x86_64-3.5/_openssl.c:3467:19: error: expected identifier or '(' before numeric constant
     static const long X509_V_ERR_HOSTNAME_MISMATCH = 0;
                       ^
    build/temp.linux-x86_64-3.5/_openssl.c:3468:19: error: expected identifier or '(' before numeric constant
     static const long X509_V_ERR_EMAIL_MISMATCH = 0;
                       ^
    build/temp.linux-x86_64-3.5/_openssl.c:3469:19: error: expected identifier or '(' before numeric constant
     static const long X509_V_ERR_IP_ADDRESS_MISMATCH = 0;
                       ^
    error: command 'gcc' failed with exit status 1

Upgrading to the latest version solved the issue and the Docker build now works.

Dockerfile

@@ -36,7 +36,7 @@ RUN apk add --no-cache --virtual build-dependencies \
     build-base \
     linux-headers \
     python3-dev \
-    openssl-dev \
+    libressl-dev \
     readline-dev \
     curl \
     postgresql-dev \
@@ -51,7 +51,7 @@ RUN apk add --no-cache --virtual build-dependencies \
     bash \
     gettext \
     ca-certificates \
-    openssl \
+    libressl \
     libpq \
     libjpeg-turbo \
     libpng \

requirements.in

@@ -1,7 +1,7 @@
 alembic==0.8.9
 boto3==1.4.4
 celery==4.0.0
-cryptography==1.7.2
+cryptography==2.2.2
 flask==0.11.1
 flask-cors==3.0.2
 flask-login==0.4.0

requirements.txt

@@ -6,17 +6,18 @@
 #
 alembic==0.8.9
 amqp==2.2.2               # via kombu
+asn1crypto==0.24.0        # via cryptography
 babel==2.5.1              # via flower
 billiard==3.5.0.3         # via celery
 blinker==1.4              # via raven
 boto3==1.4.4
 botocore==1.5.95          # via boto3, s3transfer
 cchardet==1.1.3           # via datapackage, tabulator
 celery==4.0.0
-cffi==1.11.2              # via cryptography
+cffi==1.11.5              # via cryptography
 click==6.7                # via datapackage, flask, goodtables, python-dotenv, tableschema, tabulator
 contextlib2==0.5.5        # via raven
-cryptography==1.7.2
+cryptography==2.2.2
 datapackage==1.1.4        # via goodtables
 docutils==0.14            # via botocore, statistics
 et-xmlfile==1.0.1         # via openpyxl