cleanup: fix some latent open(path).read() et al calls we previously missed

This pattern was banned by check-code way back in 1b4b82063ce2 (may of
2011), but due to a regular expression rewriting bug in check-code
these particular callsites were never detected. Python 3.7 caught the
bug, which then exposed these errors.

Differential Revision: https://phab.mercurial-scm.org/D2863

i18n/hggettext

@@ -104,7 +104,8 b' def docstrings(path):'
     """
     mod = importpath(path)
     if not path.startswith('mercurial/') and mod.__doc__:
-        src = open(path).read()
+        with open(path) as fobj:
+            src = fobj.read()
         lineno = 1 + offset(src, mod.__doc__, path, 7)
         print(poentry(path, lineno, mod.__doc__))
 
@@ -143,7 +144,8 b' def docstrings(path):'
 
 
 def rawtext(path):
-    src = open(path).read()
+    with open(path) as f:
+        src = f.read()
     print(poentry(path, 1, src))
 
 

mercurial/cffi/bdiffbuild.py

@@ -4,9 +4,10 b' import cffi'
 import os
 
 ffi = cffi.FFI()
-ffi.set_source("mercurial.cffi._bdiff",
-    open(os.path.join(os.path.join(os.path.dirname(__file__), '..'),
-        'bdiff.c')).read(), include_dirs=['mercurial'])
+with open(os.path.join(os.path.join(os.path.dirname(__file__), '..'),
+                       'bdiff.c')) as f:
+    ffi.set_source("mercurial.cffi._bdiff",
+                   f.read(), include_dirs=['mercurial'])
 ffi.cdef("""
 struct bdiff_line {
     int hash, n, e;

mercurial/cffi/mpatchbuild.py

@@ -6,8 +6,9 b' import os'
 ffi = cffi.FFI()
 mpatch_c = os.path.join(os.path.join(os.path.dirname(__file__), '..',
                                      'mpatch.c'))
-ffi.set_source("mercurial.cffi._mpatch", open(mpatch_c).read(),
-               include_dirs=["mercurial"])
+with open(mpatch_c) as f:
+    ffi.set_source("mercurial.cffi._mpatch", f.read(),
+                   include_dirs=["mercurial"])
 ffi.cdef("""
 
 struct mpatch_frag {

mercurial/posix.py

@@ -264,7 +264,8 b' def checklink(path):'
                 # already exists.
                 target = 'checklink-target'
                 try:
-                    open(os.path.join(cachedir, target), 'w').close()
+                    fullpath = os.path.join(cachedir, target)
+                    open(fullpath, 'w').close()
                 except IOError as inst:
                     if inst[0] == errno.EACCES:
                         # If we can't write to cachedir, just pretend

tests/f

@@ -61,7 +61,8 b' def visit(opts, filenames, outfile):'
             if opts.type:
                 facts.append(b'file')
             if any((opts.hexdump, opts.dump, opts.md5, opts.sha1, opts.sha256)):
-                content = open(f, 'rb').read()
+                with open(f, 'rb') as fobj:
+                    content = fobj.read()
         elif islink:
             if opts.type:
                 facts.append(b'link')