Build requires gcc

The openssl package has been split quite a while, and this package
only needs the shared library.  I'm making this change
because `openssl` today `Requires: make` which is unfortunate
for Atomic Host.

See: https://bugzilla.redhat.com/show_bug.cgi?id=783446#c4

python-cryptography.spec

@@ -9,7 +9,7 @@
 
 Name:           python-%{srcname}
 Version:        2.0.2
-Release:        1%{?dist}
+Release:        3%{?dist}
 Summary:        PyCA's cryptography library
 
 Group:          Development/Libraries
@@ -18,6 +18,7 @@ URL:            https://cryptography.io/en/latest/
 Source0:        https://pypi.io/packages/source/c/%{srcname}/%{srcname}-%{version}.tar.gz
 
 BuildRequires:  openssl-devel
+BuildRequires:  gcc
 
 BuildRequires:  python2-devel
 BuildRequires:  python2-pytest
@@ -66,7 +67,7 @@ Obsoletes:      python-%{srcname} <= %{version}-%{release}
 Provides:       python-%{srcname}
 %endif
 
-Requires:       openssl
+Requires:       openssl-libs
 Requires:       python2-idna >= 2.1
 Requires:       python2-asn1crypto >= 0.21
 Requires:       python2-six >= 1.4.1
@@ -84,7 +85,7 @@ Group:          Development/Libraries
 Summary:        PyCA's cryptography library
 %{?python_provide:%python_provide python%{python3_pkgversion}-%{srcname}}
 
-Requires:       openssl
+Requires:       openssl-libs
 Requires:       python%{python3_pkgversion}-idna >= 2.1
 Requires:       python%{python3_pkgversion}-asn1crypto >= 0.21
 Requires:       python%{python3_pkgversion}-six >= 1.4.1
@@ -159,6 +160,12 @@ popd
 
 
 %changelog
+* Sun Feb 18 2018 Christian Heimes <cheimes@redhat.com> - 2.0.2-3
+- Build requires gcc
+
+* Tue Oct 24 2017 Christian Heimes <cheimes@redhat.com> - 2.0.2-2
+- Change Requires to openssl-libs
+
 * Thu Aug 03 2017 Christian Heimes <cheimes@redhat.com> - 2.0.2-1
 - New upstream release 2.0.2
 - Modernize spec