Conditionally import ssl

Saves >=10ms on irrelevant platforms.

Author: chrahunt

src/pip/_internal/utils/inject_securetransport.py

@@ -7,18 +7,21 @@
 old to handle TLSv1.2.
 """
 
-try:
-    import ssl
-except ImportError:
-    pass
-else:
-    import sys
+import sys
 
-    # Checks for OpenSSL 1.0.1 on MacOS
-    if sys.platform == "darwin" and ssl.OPENSSL_VERSION_NUMBER < 0x1000100f:
-        try:
-            from pip._vendor.urllib3.contrib import securetransport
-        except (ImportError, OSError):
-            pass
-        else:
-            securetransport.inject_into_urllib3()
+
+# Only relevant on macOS
+if sys.platform == "darwin":
+    try:
+        import ssl
+    except ImportError:
+        pass
+    else:
+        # Checks for OpenSSL 1.0.1
+        if ssl.OPENSSL_VERSION_NUMBER < 0x1000100f:
+            try:
+                from pip._vendor.urllib3.contrib import securetransport
+            except (ImportError, OSError):
+                pass
+            else:
+                securetransport.inject_into_urllib3()